Synchronising qt-wallets (no connections) on different altcoin wallets

[x2chilleD4yAx]

I have some wallets with different altcoins. Mostly the core or qt-wallet for windows. Most of the wallets are syncing without problems, but some of them do nothing. It shows 'no connections' or '0 connections' for hours and days. At the moment, the 'bitcoin oil (btco)' and 'freecash' (both sha256 coins) don't sync. Has anybody ideas what to do?