I use whonix in qubes and I often get the:
Onion site has disconnected
The most likely cause is that the onion site is offline. Contact the onion site administrator.
Even after restarting Tor with its control panel it often just doesn’t help. I need to constantly restart tor and refresh the page to get lucky.
I’m not sure if its related, but I don’t close the tor window for days usually. Never had any issue with it on regular linux