Flat-Field Correction doesn't do anything

Two years later and this issue still persists. Maybe one day they will rework the feature and alow us to specify the calibration frame instead of trying to autodetect, which seems to be the root of the problem. 
If you try to use flat field correction with a calibration frame and a low contrast image, it just fails to detect which frame is the calibration frame then does nothing. 

Just tested flat field correction with Lightroom Classic version 13.2 on macOS 14.4.1 on 5k iMac 2019 and found that FFC can work, but success is so rare that I'd call the feature unusable.

The one way that I had FFC actually do what it promises was when I followed these steps

* quit LR including catalog optimisation

* duplicate a pair (photo+reference) twice and rename files to create a series of ref/photo/ref/photo/ref/photo

* open LrC and import the folder with the test images, then select the three pairs

* apply FFC ... and check filenames carefully: Two RAW files have been renamed to DNG ... but the original RAW files are still in the folder, LrC simply kicks them out of sight.

* sync the test folder to make the RAW files visible again.

Any other test failed, be it a repetition, a test with a sequence of photo/ref/photo/ref... or whatever.

My expectation: Adobe will fix that shaky feature asap. (I'm not going to hold my breath though)

Its now Aug. 2023 & I running LR 12.5 and this still doesn't work.

I decided to back up my preferences and did a reset. Didn't help. When I select the image and the flat-field and select Flat-Field Correction, I get a quick blink of a progress bar and then nothing.
This was working fine as of last week. Not sure what broke it. 

What was the solution? I am having the exact same issue and would like to avoid resetting my preferences if possible. I can't afford to lose my presets. 

Try resetting your Lightroom preferences:

https://helpx.adobe.com/lightroom-classic/help/setting-preferences-lightroom.html

Also see: https://community.adobe.com/t5/lightroom-classic-discussions/important-steps-for-manually-resetting-preferences-omitted-from-help-article/td-p/12972518

Quit Lightroom Classic.

macOS: Press and hold the Shift + Option keys.

Windows: Press and hold the Shift + Alt keys.

While holding down the keys, launch Lightroom Classic. 

When asked, select "Yes".