It appears that this is an issue with the Windows 10 operating system and to fix it, a system check is necessary.
Press Windows key + X and select Command Prompt (Admin) then type the following commands one at the time:
DISM.exe /Online /Cleanup-image /Scanhealth
DISM.exe /Online /Cleanup-image /Restorehealth
Secondly, you can also apply the latest Windows Updates. Press Start and type Windows Updates, then check for latest updates. Install them and then try again to set the default apps.