My iPad won’t update past 12.5.7

That's a first generation iPad Air. It, as well as any other unit on 12.5.7, isn't capable of 13 or above.

(233655)

Are you sure you have identified the model correctly? Identify your iPad model - Apple Support

iPad Air

• Year: Late 2013 and early 2014
• Capacity: 16 GB, 32 GB, 64 GB, 128 GB
• Model number (on the back cover):
• 
  
• A1474 on the iPad Air Wi-Fi
• 
  
• A1475 on the iPad Air Wi-Fi + Cellular
• 
  
• A1476 on the iPad Air Wi-Fi + Cellular (TD-LTE)—released early 2014

That appears to be a first generation iPad air and cannot be updated higher than you already have.

🤨 THE IPAD IS A AIR SILLY 🙃