Unable to open from Nextcloud

[fred-gb]

Bonjour, 👋🏻

All with docker:
Nextcloud 26.0.3
Onlyoffice 7.4.0.163
Connector 7.8.0
Traefik as reverse proxy

The URL /healthcheck give: true

In Nextcloud administration > onlyoffice, when I saved, it works and display onlyoffice version 7.4.0.163.

For testing, when I start: sudo supervisorctl start ds:example in docker, I can use OnlyOffice without problem.

But, when I create/open a new onlyoffice (any type of document), It display an blank page in Nextcloud.
Sometimes, I have a Firefox warning to open in new tab. I click on and It stucks on loading OnlyOffice.

Nothing appears in nextcloud.log when I try to load document.

What I can do?
Thanks for your help.