I got this from the support team: (after you do that, don't use the password manager to sign in, as it glitches; instead, just type your email and password to activate)
1. Quit Parallels Toolbox if it is currently running.
2. Press Command + Spacebar to open Spotlight Search, or click the magnifying glass in the top-right corner of the macOS menu bar.
3. Search for Keychain Access.app and open it.
4. On the left side of Keychain Access, under System Keychains, click on "System Roots."
5. In the search field at the top right, search for toolbox.
6. Delete the three items that appear in the results.
7. Launch Parallels Toolbox again. You will be prompted to enter your username and password.