Approach Dashticz via VPN not possible?

[Tinfinity]

Hi,

I'm very happy with dashticz. Recently I set up openVPN to enter my domoticz setup and it works very well.
I'm able to enter all websites and devices within my network.

I can also enter Domoticz in this way. However... when I try to approach Dashticz, I get a black screen, and that's it..

Do others succeed in entering dashticz via VPN?
Any idea what could be my problem and how it could be solved? Has it to do with Dashticz being a sub-folder of the domoticz installation?

Thanks!

PS also tried the beta. there it shows the loading screen and 'time-out'