Hi BunnyVonBunny,
I see you have already done plenty of troubleshooting. The error 1603 is a MSI fatal error, please use the following document to resolve the issue. Fatal Error 'Error 1603. A fatal error occurred during installation' (MSI Error 1603) Displays During HP Software Installation in Windows.
Although you have completed some of the suggest steps already, I suggest doing them again, as it is important to perform these solutions in order.
Please let me know if this resolves the issue. Thanks.
