Is the onion site down now too? Had initiated a deposit, and went to withdraw and not cant connect to the site?
I just double checked now opening Chipmixer onion website, started mixing and everything works just fine fine for me.
Are you 100% sure you used correct v3 onion website (quoted link posted above), and have you tried restarting Tor browser?
You can always Restore your Session if you saved Session Token.