Collabora doesn't work on shared directory

nextcloud 20.0.7 with collabora online version 3.8.1 [just upgraded the version but it wasn’t working in the earlier neither]

in a shared directory with upload/edit permission it is impossible to create collabora documents [.odt, .ods, .odp] while it is possible create a simple text.

if i try to create a new .odt file i don’t get any error in the graphic interface, and in the log i can only see in access.nextcloud.log a 401, while in the collabora log there isn’t nothing about it.

“GET /ocs/v2.php/apps/richdocuments/api/v1/templates/document HTTP/2.0” 401 598

any suggestion on why this is happening and how to fix this?