(I’m not from ONLYOFFICE)
I implemented to Backends for ONLYOFFICE (enaio and yuuvis).
Normally, ONLYOFFICE triggers the callbackURL after the last user (in edit mode) leaves the document (or press the save button) + a few seconds.
So I guess your that you ONLYOFFICE Instance can’t reach your callbackURL or the callback endpoint is not compatible (Method, Content-Type, Security). Do you check the log files of the DocService. Maybe it shows you more information’s about the error.
If you have still problems, it can help to add a debug proxy between your service and the ONLYOFFICE Service. So you can read the plain request and maybe find the cause of the error.
I used https://mitmproxy.org/ to check the request.
That ONLYOFFICE still shows your content is expected. It keeps the content until the last user left the edit mode and it can we witten to the backend.
A point I had my fist problems was, that the ID in ONLYOFFICE not use the same logic than my backends. A ONLYOFFICE ID for a document is only valid until the document will be closed. So it is the ID of the specific editing process.
But if you receive Force Save Callbacks (document still opened in edit mode), the ID is still valid. This kind of save operations just creates Revisions of the same document ID (relevant for the change history if you want to implement it).
So in my case, I had to implement a “Mapping” table between my documents (with versions) and the ONLYOFFICE IDs and Revisions. In this Mapping, I also saved the document changed history entries I received from ONLYOFFICE.