This is a weird issue I have been facing with XD on Windows since Sep last year. Copy-paste simply stops working using both keyboard shortcuts (ctrl+c & ctrl+v) and the mouse right click. Attempting to copy makes XD unresponsive. It takes about 5-10 mins for XD to become responsive again. But paste doesnt work even after that. This happens when tring to copy anything - text, objects, artboards etc. I can still copy-paste assets for Illustrator to XD (although this has its own weird copy issue). I tried many options listed in the XD community as well as the usual clean re-install. The main issue seems to be related to the windows UWP app framework. [the solution] - the process rdpclip.exe in windows needs to be restarted if copy-paste stops working. Method to do that is in the following link - https://windowsreport.com/copy-paste-windows-10-problems/
Thank you for reaching out and sorry to hear you are having trouble copy pasting in XD. I am unable to reproduce the same at my end on windows machine. I really appreciate your efforts in sharing the solution that worked for you. This will definitely help our customers having the similar issue.
I will also share the solution with the team to investigate on the solution that worked for you.