Hi melcasey8,
Based on the error message, it seems Teams is unable to write into those folders in your Mac because it lacks the permission. In this scenario, please make sure you use the admin account of this Mac to install Teams. Besides, you can follow the steps below
to check if it works.
1. Quit Teams.
2. Open a terminal and type:
rm -r ~/Library/Application Support/Microsoft/Teams
3. Navigate to folder Macintosh HD/Library/Application support and 'Get Info' on Microsoft folder to check if the account has the required privilege. If not, please unlock it and change the privilege to Read & Write.
4. Relaunch Teams.
While if it doesn't work, to better understand your situation, may I know when did you encounter this error, in the installation process or Teams start-up process?
Regards,
Marvin