I think Its a restore issue ( cross versions) I had a similar issue I had an old backup from about 152 and following a hard disk dying I reinstalled tried to use a 152 backup to load on a 159 (I think it was) everything restored nice but OVPN would not play the logs was giving errors about errors in the keys etc etc ,I ended up removing the OVPN and all the existing certificates etc and i then re added it as I only had two users