Problem running Collabora

Hi there,
I’ve just installed Collabora on my server and running it with the integration in Nextcloud.
When I try to open a document the engine starts loading but after a while an error message appears saying "Failed to load the document. Please ensure the file type is supported and not corrupted, and try again."
Looking to the Collabora image log on docker I can see an error relative to the opening of such a document saying: "[ lok_handler ] ERR Failed to load: file:///user/docs/61/New%20Presentation.odp, error: loadComponentFromURL returned an empty reference| kit/Kit.cpp:1149"
I’ve already checked that the nextcloud server URL was ok on the running string of Collabora and that the VirtualHost of the webserver was properly configured (even because the Collabora interface is loading into the web nextcloud interface, before getting the error message).
I haven’t find any solution on the web, I’m using Nextcloud 11.0.2 (stable) on an Apache webserver, on Debian 9.0 (strectch); in the same server I’m running Docker with the collabora/code image.
Does anyone have figured the same problems?