How can I reactivate the community studio login after it expires?
If your Community license is expired and if you try opening the studio it will ask to activate your community license. Provide your email ID with which you have done your registration for the first time and activate it. This will help you in resolving this issue.
Is the email ID set when registering for platform.uipath.com account?
yes you better to have that email and just go through if any details ask
then your CE will automatically reactivate to next time period