When trying to mount SMB share using gio you might encounter the following error:
$ gio mount smb://ptnas1.cellebrite.local
gio: smb://nas.corp.local/: Location is not mountable
This error might be due to a missing gvfs backend. The smb backend should be located in /usr/share/gvfs/mounts/smb.mount. If it is missing, you should install the gvfs-backends package and it should resolve the mounting issue.
If the mount was successful, but you can’t see it under $XDG_SESSION_DESKTOP/gvfss/, you are probably missing the FUSE server that makes the mounted filesystem available to all applications and not only to GIO aware applications. You can install the FUSE server by installing the gvfs-fuse package. The server will automatically run after reboot. If you want to start the server immediately, you can start it manually:
$ /usr/lib/gvfs/gvfsd-fuse /run/user/1000/gvfs