Synchronize Clips in FCP X is suddenly not working
I have been using FCP for 13 years and FCP X for the last 3 (currently 10.4.8). I use synchronize clips all the time to link audio from zoom H4n to 4k footage (Sony A7iii) but all of a sudden last week it just stopped working correctly and can't sync anything. I thought it might be my OS so I just upgraded to 10.15.5, but it did not help. Any thoughts?
MacBook Pro 15″, macOS 10.14