I edited 832 CR3 raw files in Lightroom, got to the end of the edit and went to export to DNG (Uncompressed), the export dialogue appeared, hit export, progress bar appeared top left but nothing beyond that happened.
I restarted Lightroom and it worked fine on the next attempt.
This has been a regular occurence and a sporadic one at that.
When it happens again, see if exported files are appearing in the chosen export folder (even though the progress bar isn't moving). That's been observed in some other situations, and it would help troubleshooting to know if that's occurring to you.