This usually means the MSYS2 UCRT64 toolchain is not on PATH.
Use the UCRT64 shell or export the path before running the build:
export PATH=/ucrt64/bin:$PATH- Confirm the DLL is copied into the Notepad++
pluginsdirectory. - Restart Notepad++ after copying the DLL.
- Check that the DLL name matches
MarkdownHeaderList.dll.
- Make sure the active file contains Markdown ATX headings that start with
#. - Confirm the headings are not inside a fenced code block.
- Save the file before testing refresh behavior.
- The parser expects UTF-8 text.
- Save the file in UTF-8 if headings contain non-ASCII characters.
- Restart Notepad++ after changing the system theme.
- Reopen the panel so the plugin can re-read the current theme state.
- Edit the file and save it.
- Switch to the tab again if multiple documents are open.
- Reopen the panel if the tree still does not refresh.