You can’t run Instagram Reels longer than 90 seconds as video view ads through Facebook Ads Manager.
Reels ads are limited to vertical videos that are 90 seconds or less, so even if you upload a 5–10 minute Reel organically, Meta won’t allow it to run in Reels ad placement.
If you want to promote long-form content, you’ll need to use other placements like Facebook Feed, Instagram Feed, or In-Stream video.
Alternatively, you can trim your long video into shorter clips under 90 seconds and run those as Reels ads to stay within platform guidelines.