wallet is still on maintenance.
Well, 6 months is definitely a long time. But this is exactly what everyone expects by this point from yobit, which has been historically extremely crappy with all of their clients. I did some research and found that at least some people have the same issue as you, 5 months back: https://www.reddit.com/r/coinmagi/comments/7px3vl/yobit_exchange_xmg_wallet_maintenance/
There is nothing wrong with your deposit (if you can verify that your deposit address is correct), since there has been tons of confirmations already.
Don't bother PM'ing yobit, they will just ignore you.
I honestly don't know what else you should do other than just play the waiting game. I'd actually consider my coins gone by this stage, simply because yobit's support is one of the most unresponsive ones out there. But you should keep bumping your old tickets, and write new ones, just to hopefully remind them. After all, they do hold your coins in one of their addresses, that they own.