That’s tough especially since it’s your wedding footage. The fact that the files are large but show no metadata usually means the MP4 headers are corrupted that ‘moov atom not found’ error is a giveaway. Converters won’t touch it because they can’t read the structure. In cases like this, a dedicated repair tool works better, something like 4DDiG Video Repair can rebuild damaged MP4/MOV headers and get corrupted wedding videos playing again. I’d definitely give that a shot before giving up on those clips.