If no preview is shown after the plugin is installed, find the solution here if you're running on Ubuntu 24.04 server.

[lifeboy]

When I click on the area where the preview should be shown, it displays the document name.

I have tested with Firefox and Chromium. Both do the same. No preview.

Environment:
Redmine version 6.0.5.stable
Ruby version 3.2.3-p157 (2024-01-18) [x86_64-linux-gnu]
Rails version 7.2.2.1
Environment production
Database adapter PostgreSQL
Mailer queue ActiveJob::QueueAdapters::AsyncAdapter
Mailer delivery smtp
Redmine settings:
Redmine theme Alternate
SCM:
Git 2.43.0
Filesystem
Redmine plugins:
redmine_advanced_checklists 2.4.0
redmine_banner 0.3.4
redmine_charts_plugin 1.0.0
redmine_kanban 2.5.6
redmine_mail_ticket_sync_pro 0.0.1
redmine_more_previews 5.0.9

Version: 24.2.7.2 (X86_64) / LibreOffice Community
Build ID: 420(Build:2)
CPU threads: 8; OS: Linux 6.14; UI render: default; VCL: gtk3
Locale: en-ZA (en_GB.UTF-8); UI: en-ZA
Ubuntu package version: 4:24.2.7-0ubuntu0.24.04.4
Calc: threaded

[lifeboy]

I also compared systems:

My laptop:

# System Details Report
---

## Report details
- **Date generated:**                              2025-08-12 18:55:54

## Hardware Information:
- **Hardware Model:**                              ASUSTeK COMPUTER INC. ZenBook UX425EA_UX425EA
- **Memory:**                                      16.0 GiB
- **Processor:**                                   11th Gen Intel® Core™ i7-1165G7 × 8
- **Graphics:**                                    Intel® Xe Graphics (TGL GT2)
- **Disk Capacity:**                               512.1 GB

## Software Information:
- **Firmware Version:**                            UX425EA.319
- **OS Name:**                                     Ubuntu 24.04.2 LTS
- **OS Build:**                                    (null)
- **OS Type:**                                     64-bit
- **GNOME Version:**                               46
- **Windowing System:**                            Wayland
- **Kernel Version:**                              Linux 6.14.0-27-generic

A remote machine I use:

# System Details Report
---

## Report details
- **Date generated:**                              2025-08-12 18:54:34

## Hardware Information:
- **Hardware Model:**                              QEMU Standard PC _i440FX + PIIX, 1996_
- **Memory:**                                      20.0 GiB
- **Processor:**                                   Common KVM processor × 12
- **Graphics:**                                    Software Rendering
- **Disk Capacity:**                               236.2 GB

## Software Information:
- **Firmware Version:**                            rel-1.16.1-0-g3208b098f51a-prebuilt.qemu.org
- **OS Name:**                                     Ubuntu 24.04.2 LTS
- **OS Build:**                                    (null)
- **OS Type:**                                     64-bit
- **GNOME Version:**                               46
- **Windowing System:**                            X11
- **Kernel Version:**                              Linux 6.8.0-48-generic

Both don't load the preview.

[lifeboy]

And here is what my log shows on the Laptop:

I, [2025-08-12T18:43:18.353854 #335586]  INFO -- : [99f560cb-2248-4884-9ad7-a00757ee7866] Started GET "/attachments/more_preview/2/index.html?reload=1" for 192.168.132.5 at 2025-08-12 18:43:
18 +0200
I, [2025-08-12T18:43:18.355179 #335586]  INFO -- : [99f560cb-2248-4884-9ad7-a00757ee7866] Processing by AttachmentsController#more_preview as HTML
I, [2025-08-12T18:43:18.355292 #335586]  INFO -- : [99f560cb-2248-4884-9ad7-a00757ee7866]   Parameters: {"reload"=>"1", "id"=>"2"}
I, [2025-08-12T18:43:18.361114 #335586]  INFO -- : [99f560cb-2248-4884-9ad7-a00757ee7866]   Current user: admin (id=1)
E, [2025-08-12T18:43:18.377947 #335586] ERROR -- : [99f560cb-2248-4884-9ad7-a00757ee7866] Creating preview with Libre failed (pid 340493 exit 1):
Command: cd '/tmp/d20250812-335586-mokog7'; soffice --headless --convert-to html --outdir '/tmp/d20250812-335586-mokog7' -env:UserInstallation=file:///tmp/d20250812-335586-k0lyfa/user_installation '/var/www/redmine/files/2025/08/250812155622_24f3908ce5308eea298d34447f4cd859.ods'; mv './250812155622_24f3908ce5308eea298d34447f4cd859.html' '/tmp/d20250812-335586-mokog7/index.html' 
E, [2025-08-12T18:43:18.378486 #335586] ERROR -- : [99f560cb-2248-4884-9ad7-a00757ee7866] An error occured while generating preview for /var/www/redmine/files/2025/08/250812155622_24f3908ce5308eea298d34447f4cd859.ods
E, [2025-08-12T18:43:18.378556 #335586] ERROR -- : [99f560cb-2248-4884-9ad7-a00757ee7866] Exception was: RedmineMorePreviews::Exceptions::ConverterShellError
E, [2025-08-12T18:43:18.378791 #335586] ERROR -- : [99f560cb-2248-4884-9ad7-a00757ee7866] /var/www/redmine/plugins/redmine_more_previews/lib/redmine_more_previews/conversion.rb:340:in `command'

It seems this is crux of problem: Exception was: RedmineMorePreviews::Exceptions::ConverterShellError

What is that and how can that be fixed?

Update: I also noticed this in the README.md

LibreOffice must be reachable with "soffice" to the user, the redmine service is executed by.

I have test with different users. Libreoffice is installed for all users on the machine. Anyone can do "soffice" and Writer loads.

Not sure why a red exclamation mark icon is displayed with the message?

[lifeboy]

It just dawned on me that the sentence LibreOffice must be reachable with "soffice" to the user, the redmine service is executed by. implies that Libreoffice must be installed on the machine that Redmine is running on?! In other words, this preview capability is not a feature of the browser that displays the server contents, but it's actually output generated on the server in html or image format.

If this is so, and the Redmine server is headless, then does Libreoffice function correctly?

Surely this has been discussed or mentioned before? Almost no servers have GUI's installed and why should they?

[lifeboy]

UPDATE: After having a look at the what the ruby source code reveals, I saw the it uses "soffice --headless" to do the conversion. So I installed LibeOffice using dpkg, and then tested it manually, which revealed the LibreOffice 24.2.7 has a regression error preventing --headless to work correctly.

So, after installing LibreOffice 25.2 from the LO website, I get the following:

(Seriously devs? Punctuation matters! When you write "Libreoffice available" it means it was found. If you mean to say "Is Libreoffice available?" then you need to say it like that. Our time is also valuable)

However, now Redmine crashes, but I'll open a new issue for that.

[lifeboy]

I reopened the issue since I found issue mentioned here and Redmine doesn't crash anymore. However, the original problem remains. The converted output from Libre is not showing and neither is the Peek output from pdf's.

So I have now configured things a little differently.

These have to be set (left the help visible for clarity's sake):

Now the converted previews show in the iframe. I selected pdf for most document type, since most of the others (like .html) do lose a lot of detail in the conversion process.

There's just the above problem remaining. The "loading" notification never goes away.

How can that be fixed?