Our Onlyoffice server crached so decided to test the built-in code server and Nextcloud Office.
They are installed on the same server (no docker) and Nextcloud Office reaches the code server (at least it gives a green light). When clicking on a document it does not open, only download. No error in the log.
Sadly enough your post is missing almost all specific technical information. Thanks for your post, but please take a little time to get acquainted with the forum and make a stronger effort to troubleshoot. It is the least you can do when asking others to help you:
Search your question as keywords on this forum. If you find something useful, link it directly into this post.