OnlyOffice certificate problem

I have a small problem with my OnlyOffice installation.

After runing my ansible playbook OnlyOffice is working just fine.

If I go to the OnlyOffice settings page to add txt or csv files and save the changes I get an timeout error at the top of page. And after that the OnlyOffice app is permanent disabled.

In the logs I find error messages saying that Nextcloud can’t verify the certificate.

If I go to https://my-domain:8443/ I’m still getting a correct “Welcome” page with a valit letsencrypt certificate.

Have you tried to use the full_chain in the OnlyOffice config?

Thanks. That was the solution. Now it works.

Just now I want to run OnlyOffice with selfsigned certificates.
The certificates are generated with this docker container:

How do I assemble a fullchain certifcate from the single files created by this container?
I tried key + cert + ca.cert but that didn’t work.