Have you tried asking him to work from home? It's possible he's scared of Covid but doesn't want to say that. Perhaps if you suggest he can work from home you would get some useful work out of him.
Otherwise, as noted above, he's not accumulated enough paid sick days to be paid if he started in June, so you can just stop paying him.
We had an employee like this a few years back. He had a mental health issue. But again, just vanished, didn't communicate etc. It took months to let him go because we could not even find him (he went home to India without telling us). These kinds of things can be really tricky. I think you have to do as much as you think is reasonable (karma is a bitch) but when it's all just too much, you have to let him go.