Call the gym and ask after him - maybe he's caught Covid and is really sick. When I got Covid I literally had to text a coworker from bed to ask her to let work know I couldn't work. The email I sent one day saying I'd be out was disjointed and made very little sense (Joseph covid sick no out work sick).

Now

I prepaid for some personal training sessions at the gym, and I was contacted by a trainer.
We have been trying to work out a time to meet, and I haven't heard back for a few days. How long should I give this person before looking for a new option?