Why can't I install iOS 15?

I cleared the appropriate amount of space on my phone to download iOS 15 and it WILL NOT INSTALL. It verifys the update for 5 minutes and then sits on the software update screen until it says "There was an error while checking for a software update". This is really frustrating and I already googled help which told me to reset my network settings which just made my phone forget every wifi its been connected to so thanks for that. HELP ME!!!!