I recently updated to Negative Lab Pro 2.1 and since then have been getting the following error when running the TIFF Scan Prep utility which is now recommended.
I’m running it on Windows 10 with Lightroom Classic CC 9.1, Camera Raw 12.1 with GPU acceleration set to Auto.
I’ve just made a quick update to v2.4.1 that includes a fix to at least one issue with the TIFF Scan Prep. Could you give it a try and see if this resolves the issue for you?