Codec for Instagram?

Hi everyone, I've been having issues uploading an H264 to Instagram. It really heavily reduces the quality. This is for a 4 minute 1080p video.

Edit for AutoMod:

• System specs: Mac Pro 5,1 - 2x3.33Ghz, 48GB RAM, RX 580 8GB

• Software specs: Resolve 17, Avid Media Composer 2018

• Footage specs: H264, MP4 Container

SOLVED: This is embarassing, but the client was sending the video to herself via iMessage; saving to her phone and then uploading that way. Of course iMessage compressed the video. Solved now, thanks everyone.