NAS 424 server Online VPN disconnected

We are having some problems with a NAS 424.

The readycloud is used on a Windows 10 and Macbook without any problems. Recently we bought a new Macbook (with the same softwareversion Catalina 10.15.5) and now with the new Macbook the Readycloud app doesn't work. 

Whe we start up the old Macbook again it does synchronize via LAN and WAN and the new MacBook only syncs via LAN. A reboot of the NAS didn't make any differance.

Also switched of anti virus/firewalls, logged off and logged on again in the app  etc. but still we ge get the message " Online (VPN disconnected).

Has somebody got the same problem or even beter a sugestion how to solve this??

Thanks in advance.