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)

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 🙃

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