I had to send the S9 back and get a replacement as the suction stopped working
it could be the motor itself or the actual duckbill. i had a few times where it would stop suctioning even though everything was in place properly. turned out the duckbill had ripped and wasn’t sucking anymore
I have the momcozy s12 Pro and sometimes they don’t suction. I find that if the diaphragm is wet, it stops them from working properly.
which momcozy do you have? i had the 9 and i had similar problems. i ended up getting the momcozy m5 and they are much better