First thing to do is to take off shield to get at screw slot. Make sure it turns both ways. Try again.A small thing can jam and it will not make a noise. Turning usually frees it up.It uses a circuit breaker, no fuse
Yep, keelhauler has the right advise.Make sure to put only #1, #2, and toilet paper down the toilet. No feminine napkins or other items because they will jam the macerator but good. You don't want to be cleaning it out by hand. A guest/visitor might not understand the reason for the rules. Make sure they understand and follow them. Also provide them a friendly-use garbage can in the bathroom.