SnapGene is not guaranteed to be compatible with every Window Manager/Desktop Environment available for Ubuntu. It's not feasible for us to test and support every variation.
Seethe following FAQ article for information on supported versions of Ubuntu - What are the System & Hardware Requirements for SnapGene?
If your new SnapGene installation will not start on a supported version of Ubuntu then first ensure you are using the Gnome Window Manager (Consult Ubuntu documentation for instructions on how to switch Desktop Environments). If you still can't start SnapGene when running under Gnome then submit a support request via https://support.snapgene.com.