There is still no other complains besides you OP. They undergo maintenance yesterday based on there telegram announcement channel for no stated reason.
Dear Users!
Please be informed about short maintenance from 13:45 (GMT).
We are sorry for the inconvenience.
Mercatox team
But they already finish same day.
Dear users!
Maintenance work successfully completed.
Service is fully accessible.
Good luck in the forthcoming trades.
Mercatox team
So maybe that issue they face yesterday is the reason for the delay in deposits/withdrawal process. Take note that this is just my assumption.
It's better to post this concern on their ANN thread so that they will notice you or everyone will be aware on what's going on to avoid potential loss.
Mercatox ANN thread:
https://bitcointalk.org/index.php?topic=1662702.780Mercatox TG Channel: @mercatox_official