Thank you for reaching out and sorry to hear that you're having trouble using color picker. Would you mind sharing the OS version of your machine? Have you tried signing out of XD and Creative Cloud app, restart the machine and then sign back in? Can you confirm Is it Issue happening with every file or with a specific file? Also Is it happening only with Xd or any other Adobe app?
We're sorry for the inconvenience. please feel free to update this discussion in case you need further assistance and we will be happy to help.