To have something to compare with, try to open the certificate of this site.
When you look at the address in your browser, it is: https://technicalhelp.de
Open up the certificate, go to the details page and find the Subject line.
It says: CN = http://www.technicalhelp.de
Also take a look at the Subject Alternate Name, there you have:
DNS Name=www.technicalhelp.de
DNS Name=technicalhelp.de
Now compare this to your own certificate. What you use as address for your RDWeb server must match the Subject CN in your certificate for ThinOS to accept that the Certificate is OK for your RDWeb server. Some browsers also check the Subject Alternate Names. and at least one DNS Name entry must match as well.
If these two things do not match your Servers address in the Certificate you have installed, the connections will not work correctly. Other things in the Certificate, like issue and expire times must obviously also be OK.
If everything looks OK in a Web Browser when you inspect the Certificate, download it from there (Copy to File) and export in DER encoded format as a .CER file and use that as ConfGen instructed.
Hope it helps.
/Frank