Sims won´t use sink?

Do you have any custom sinks or such that may interfere with normal functioning of sinks?

This happens in my game as well. It has to with setting the sink type to kitchen or bathroom. For me, i think, it started happening once I change an existing sink for a new one in build mode. But I can't exactly pinpoint it. Setting sinks back to be usable for both kitchen and bathroom will likely fix this issue. But then sims will also do dishes in the bathroom again 🙃

When this happens in my game it is usually when a sim has put a plate somewhere weird that they can't reach. I have to put the all the walls up and have a look around to find the errant plates and drag them to where they can be reached or just straight over to the sink.

It is very annoying, I don't know why they can place plates in unreachable locations in the first place.

It doesn´t matter where the plates are in the house, they refuse to use the sinks 😶

Have you tried replacing the sinks or maybe reset both sinks and sims? 

Do you have any low hanging lights or cabinets, etc. over the sink? I've found that will cause routing issues.

I had that problem too some days ago and the low hanging cabinet was the reason.

Does it happen if you put a free-standing, accessible sink in the middle of the room with nothing near it or above it and with MOO turned off when placing it, then assign it as a kitchen sink? Does it happen on different lots in this save? Does it happen in a fresh save?
Can you share a screenshot (with all walls up around it) of the sink and any thought bubble they have when you tell them to wash a dish after designating all other sinks as bathroom and this one as kitchen (move the dishwasher to household inventory for this test)?

In some of my households I don´t even have cabinets so it can´t be that 😶

No, no cc sinks what so ever.