Which coin ? I know there are a couple of wallets out of the 726 wallets they have that currently have some issues that are being resolved. I'm only an unpaid chat moderator there so I don't have access to support tickets . The admins don't go on Bitcointalk so it won't get resolved by posting it here. They have over 500 000 registered users so you can imagine that the amount of daily support tickets is huge.

Cryptopia has many more new users and small users than some of the other exchanges. A lot of small new users are attracted by the site rewards and tip bot. This means that while their overall volume may e lower than other exchanges - their servers are just as busy or busier. The amount of small tx's means that sometimes wallets are unable to cope with the volume of transactions and need to be restarted. Cryptopia is currently ranked #6 in crypto to crypto volume while their overall volume value is only #39.

Sycronising a large wallet takes much longer than a personal wallet that only has a few transactions - especially when the coin network itself may be struggling with high demand.

Please let me know what coin and I'll see what is happening.