For it-tects to help you via TeamViewer, TeamViewer needs three one-time permissions on your Mac: Screen Recording, Accessibility and Full Disk Access. You need the password of an administrator account on the Mac.
Steps
Open TeamViewer. In the menu bar, choose Help › Check system access.
In the window, click the button next to the first permission. System Settings opens at Privacy & Security.
Turn on the switch for TeamViewer and enter your Mac password. If TeamViewer_Desktop is also listed, turn it on as well.
Repeat these steps for the other two permissions.
If macOS asks, restart TeamViewer with Quit & Reopen.
Tip: If TeamViewer is missing from the list, click + at the bottom, select TeamViewer in the Applications folder and click Open.
Note: If it-tects only sees a black screen, the Screen Recording permission is missing. If mouse and keyboard can't be controlled remotely, Accessibility is missing.