No module named 'serial

[jacopsd]

HA Core 2024.4.4
HA OS 11.5

Suddenly these errors appear in the log, and the module doesn't work anymore:

  File "/app/./modbus2mqtt.py", line 2, in <module>
    from  modbus2mqtt.modbus2mqtt import main
  File "/app/modbus2mqtt/modbus2mqtt.py", line 33, in <module>
    import serial
ModuleNotFoundError: No module named 'serial'

Tried 'pip install pyserial' in the console, but that doesn't work