Hey PostOak,
Do you have access to a PC or Mac with the Battle.net desktop app installed?
This may be caused by having too many sent friend requests that are pending. Unfortunately the only way to check pending sent friend requests is through the desktop app, can’t do it on mobile.
If you can get to the desktop app go to the Friends list and click the Cog wheel icon in the top right, then go to View Sent Friend Requests. If that has tons in there try clearing them all out and then try sending friend requests again on mobile.