Lightroom cc 7.4 regular develop presets (left panel) won't do anything

You have this problem of having 'upgraded' a perpetual license of Lightroom 6 to Lightroom Classic somehow. That upgrade should never have been possible, because you do not have a subscription to Lightroom Classic, but a perpetual license for Lightroom 6. There is no perpetual license for Lightroom Classic and there is no Lightroom 7. Due to a bug in the updaters it was somehow possible to install Lightroom Classic without having a subscription, and this now causes all kinds of problems. You’ve just been lucky that it didn’t happen earlier, when you first started with the upgraded version.

The solution is to go back to Lightroom 6, the version you have a license to use. In order not to lose all the work you may have done since your first update, select all the images that were imported after you updated to Classic and choose 'Metadata - Save Metadata to Files'. Then open Lightroom 6 with your old Lightroom 6 catalog, and import these images. The edits and metadata should come over, except those edits that are new for Lightroom Classic (like Range Mask). You can find the correct installers and updaters here:
https://helpx.adobe.com/lightroom/kb/...

Or, of course, you can take a subscription to Lightroom Classic after all. In that case you need to fully uninstall Lightroom, and then reinstall it after the subscription has come into effect and you’ve logged in with your Creative Cloud credentials. Your catalog will not be affected by uninstalling/reinstalling.

Also please go here to help Adobe sort out this mess: https://helpx.adobe.com/creative-clou...