I face the Invalid License error message when entering my license key / using Tetra4D trial version.
In recent Acrobat Pro versions (2020 and DC Continuous Relase) a new default option prevents most third party plug-ins from working correctly.
Please make sure that the default Adobe Acrobat Pro setting in Edit → Preferences → Security (Enhanced) → “Enable Protected Mode at startup” is DISABLED. Then restart Acrobat and enter your license key if asked to.
If you still face the error message please contact the Support Team.
Regards,
Tetra4D Support Team