This error can occur if you are using running SnapGene on a computer account that previously had SnapGene installed and running with an older Sassafras-based shared license.
To fix this issue do the following:
macOS
1. Quit SnapGene.
2. Type command-space (Spotlight Search) and search for the phrase "terminal". Hit return to run the Terminal application.
3. Copy and paste the following command (one line) into the Terminal window and hit return.rm ~/Library/Application\ Support/SnapGene/.klf
4. Run SnapGene and attempt to register using the new credentials.
Windows
1. Quit SnapGene.
2. Click the Windows button and search for the phrase Command Prompt and run the "Command Prompt" program.
3. Copy and paste the following command (one line) into the Terminal window and hit return.
del /AH %AppData%\SnapGene\.klf
4. Run SnapGene and register using the new credentials.