Though deposits seem not to work, my test deposit of 50BTM from 2 days ago still doesn't show up.
Do yourself all a favour and test first with a small amount before moving big chunks of BTM to Polo!
It works, but you have to open support ticket on Polo, and then Polo staff will increase you balance manually.
I don't know why they are doing it manually, but that is procedure for now.
Oh well - thanks for the hint, will do that and hopefully Polo's support is quicker this time than last time I needed them.
But otherwise I'll stick with the other exchanges that automatically process deposits...