zoom keeps saying unsupported format

Hi guys I keep receiving this "zoom keeps saying unsupported format". I'm trying to get the video in advanced so I can record myself. I did one video ok, but then the second one it gave me this...tried to re-installing zoom, still the same.

Any idea why this? shall I convert the MOV (done on an  i phone)? I also tried to turn the video (from vertical to horizontal, then re-saved it and still can't do it). I guess my only option is to share the screen and record myself? 

Please let me know! Thank you Gaia