Steps to reproduce:
1. Open Hub
2. Click Preferences > Licenses > Add > Get a free personal license
3. Create an empty 3D project and then close it
4. Try opening the newly created project from the Projects list

Expected result: project opens
Actual result: project doesn't open

Reproducible with: 3.1.2
Not reproducible with: 2.4.5

Workaround for this issue:
1. Completely close the Hub - right-click on the Hub icon in your system tray and select "Quit Unity Hub"
2. Backup and delete the license file "Unity_lic.ulf" located in "C:\\ProgramData\\Unity"
3. Generate license request for manual activation in Hub (Hub > Preferences > Licenses > Add > Activate with license request > Create license request)
4. Open that .alf file in your preffered text editor and add the following line into <MachineBindings> section: “<Binding Key="4" Value="" />” without the quotation marks
5. Now proceed with activation and upload the modified .alf file to get the license
6. Activate the license

Notes:
- Users are usually able to create a new project, however, after closing it, they are no longer able to open it
- Sometimes, but not always, an error message appears: "No valid Unity Editor license found. Please activate your license\!"
- Users reported the same issue regardless of the method used in activating a license
- Noticed this happening to Windows users only