The white pipe under the sink that looks like a J is where the clog is (95% of the time). It is held on by 2 threaded pieces of pipe.
Take everything out from under the sink. Get a bucket big enough to hold all of the water in the sink. Plug the sinks (less water to drain). Unscrew the two parts of th J trap. Try to catch as much water as possible in the bucket, but have a towel handy. Now, take the trap that you just removed and clean it out. Then put it back on the sink and screw it on again.
Now, unplug your sinks and the water should flow.
https://www.plumbingsupply.com/how-to-clean-a-sink-trap.html
I tried it! But the pipe ended up to be clean. I guess the clog must further along.
Wow!!
Say Hi to the plumber for us. :-(