Please uninstall and reinstall STAAD.Pro along with RCDC. While installing, right-click on the installation file and select the option "Run as administrator" (though you may be the administrator for the machine).
I resolved this problems uninstalling and installing again as ADM
It didn't work for me. I tried doing Windows update, uninstall STAAD.Pro and RCDC but the problem is still the same.
I installed it as ADM btw
It is working now after I installed STAAD.Pro CONNECT Edition Update 3, I also installed RCDC from the online installer of STAAD.Pro CE Update 3. Thanks!