in the mattemost log I find the following messages:
mai 13 14:38:29 mattermost[3518]: {"level":"info","ts":1620909509.3354337,"caller":"mlog/sugar.go:21","msg":"WOPI file info loaded successfully!","plugin_id":"com.collaboraonline.mattermost"}
mai 13 14:38:25 mattermost[3518]: {"level":"info","ts":1620909505.0383484,"caller":"app/plugin.go:286","msg":"Syncing plugin from file store","bundle":"plugins/com.collaboraonline.mattermost.tar.gz"}