Hi,
I had a bug Ā« a bit similar Ā» : I could not save the Onlyoffice app settings in Nextcloud with NC and OO in 2 docker containers in the same machine (network mode bridge). My error message was a bit different : Ā« bad health check Ā» or Ā« error while downloading the document being converted Ā».
I could resolve it with adding the local IP and Domain names of both nextcloud and only office in the Ā« trusted domains Ā» array in NC config.php : [Onlyoffice] Error while downloading the document file to be converted ou encore ici : https://github.com/ONLYOFFICE/onlyoffice-owncloud/issues/181
So now I can save the settings !
But I still canāt open OO documents : when I click on a .docx doc in Files for example it says Ā« onlyoffice unreachable Ā».
I also found a page that could help : https://api.onlyoffice.com/editors/nextcloud
@edvinkuric and @syrosh what did you put in the 3 server fields Ā« external doc server Ā», Ā« internal doc server Ā» and Ā« internal NC server Ā» ? It could help to understand the pb