For the Activity issue, here is the solution:
Make sure you have the UiPath.Mail.Activities package installed. If you dont have that, then go to Manage Packages → All Packages. Then search for the package. Click the Install Button and then click Save.
After the package and dependency is successfully installed, The activity will be under Installed → Integrations → Gmail and Outlook
If this solves your issue, do mark it as a solution.
Thank You
Happy Automation 