Welcome to the Magix Sound Forge users community @david-s2501.

Is the PC connected to the internet? it needs to be connected occasionally to update codec licensees.

Otherwise try to reset SF and clear the cache in the 'File' menu.

If that does not work, your could try deactivating and re-activating.

Otherwise, uninstall and reinstall. It is 'usually' best to uninstall using a third-party uninstaller that can remove the left-over registry entries and other pertinent data the OS uninstall leaves behind, which can cause the issue to reoccur.
Revo Uninstall has a pro and freeware versions. The free version is adequate in most cases.

You can also upgrade to Sound Forge 16, you will get an upgrade discount using your SF-13 serial when purchasing the upgrade.