I have done the following: 1. Quit XD and restart it. 2. Uninstall and reinstall XD. 3. Sign out of the XD and Creative Cloud app, restart my machine and then sign back in.
*I still have the problem.* - Yes, I can change the font-weight in any other application - I separated fonts in Adobe XD instead of displaying them under the font-weight dropdown.
*Note:* I have the version of OS Windows 10 *Home*, 21H1 Edition: Windows 10 Home Version: 21H1 Installed: on 8/5/2021 OS build: 19043.1151 Experience: Windows Feature Experience Pack 120.2212.3530.0