> Until now it worked fine, but after a koha upgrade in 20.11.x, it is stuck with the status disabled and it won't activate.

Just a guess: is the is_enable code correct?

https://github.com/DSI-Universite-Rennes2/koha-plugin-warehouse-request/blob/master/Koha/Plugin/Fr/UnivRennes2/WRM.pm#L310

Julien, we got this one on, though we don't use it right now. This could explain it's working with our 20.11 ?