I use Installshield 2023. I had simply replaced the set of .dll's that our Installshield project is configured to read from that were more recent and that I wanted included in the install. I then clicked Build in InstallShield as I always have. No other settings or project configurations were changed.

Out of nowhere, I am encountering the error -6421: An error occurred determining if the setup [Our MSI] is a major upgrade. I first restarted the PC, and that did not fix the issue. I then deleted the whole Temp directory, and that also did not fix the issue. There is no further documentation available that I can see, so I am hoping that someone can provide a resolution or additional troubleshooting tips for this.

Thanks.