The problem with VPN is that they can't be fixed by a 3rd party. Only the developers of those servers have access to personal logs and network info. Basically, you will have to contact the server admins and provide logs (if possible per their instructions). In case there is something wrong with their servers, you will be notified.
Additionally, the ISP you're using might block your connections to the VPN's servers. Contact them and explain that it's work your and they should avoid blocking or terminating connections because they might consider illegal traffic or something related.