Ive got 2 dash cams (different makes) One works perfectly fine, the other , despite appearing to be recording - has no video files. (same issue using different sd cards) However , it gets odder because it DID actually record just 1 video , which was my last car restart. After that back to no more vids recording.
check to see if there is a firmware update which might correct the problem. how old is it & how long has this been going on?