Reels require the video to be at the highest quality.
Top right corner of your Instagram profile > Settings and privacy > My apps and media > Data usage and media quality > Enable high quality uploads
1️⃣ Go to Instagram > Settings and privacy
Select “Settings and activity” from the top right menu of your Instagram profile.
2️⃣ Data usage and media quality
Select the Data Usage and Media Quality menus.
3️⃣ Upload at highest quality
Enable 'Upload at highest quality'.
