I am also having this issue. Wanted to have some music on a Mac to use in Music Assistant. I tried my admin, login, and even added a shared user to the folder. I can see it from another Mac just fine but HA refuses to mount the folder: cifs_mount failed w/return code = -13 Permission denied.
DEBU[0000] Response body="{\"result\":\"error\",\"message\":\"Mounting Multimedia did not succeed. Check host logs for errors from mount or systemd unit mnt-data-supervisor-mounts-Multimedia.mount for details.\"}" fields.time=254.338125ms headers="map[Content-Length:[178] Content-Type:[application/json; charset=utf-8] Date:[Thu, 26 Feb 2026 15:32:16 GMT] Server:[Python/3.13 aiohttp/3.13.3]]" received-at="2026-02-26 16:32:16.200927219 +0100 CET m=+0.264625212" request="&{POST http://supervisor/mounts HTTP/1.1 1 1 map[Accept:[application/json] Authorization:[Bearer ] Content-Type:[application/json] User-Agent:[go-resty/2.17.1 (https://github.com/go-resty/resty)]] {} 0x2005a0 178 [] false supervisor map[] map[] <nil> map[] <nil> <nil> <nil> {{}} <nil> [] map[]}" status="400 Bad Request" statuscode=400
Error: Mounting Multimedia did not succeed. Check host logs for errors from mount or systemd unit mnt-data-supervisor-mounts-Multimedia.mount for details.