If TightGate-Pro is used via a Citrix server and thin clients are used, it can happen that the transfer of umlauts via the clipboard does not work correctly. Check the following:
In the Citrix configuration file All_Regions.ini in the section [Virtual Channels\Keyboard] the parameter UseEUKS to 1 must be set:
[Virtual Channels\Keyboard] UseEUKS=1
The following link may also be helpful:
https://wiki.openthinclient.org/omd20191/openthinclient-manager/anwendungen/citrix-client