Apple is no longer signing iOS 13.5.1 - 17F80 for 36 devices

If you are using any of the devices below, note that Apple has topped signing of the iOS 13.5.1 for them. Check out the list to see if your device is among. And if that be the case, not that you won't be able to restore any iOS 13.5.1 ipsw firmware file using iTunes.

But there is a newer iOS version (iOS 13.6) for the devices on which the iOS 13.5.1 has stopped being signed.

iOS 13.5.1 - 17F80 stopped being signed for these devices

iPads

1. iPad Air 3 (WiFi)
2. iPad Air 3 (Cellular)
3. iPad Mini 4 (Cellular)
4. iPad Air 2 (WiFi)
5. iPad Air 2 (Cellular)
6. iPad 5 (Cellular)
7. iPad Pro 9.7-inch (WiFi)
8. iPad Pro 9.7-inch (Cellular)
9. iPad Pro 12.9-inch (WiFi)
10. iPad Pro 2 (12.9-inch, WiFi)
11. iPad 7 (Cellular)
12. iPad Pro 2 (12.9-inch, Cellular)
13. iPad Pro (10.5-inch, WiFi)
14. iPad 6 (WiFi)
15. iPad Pro 4 (12.9-inch, Cellular)
16. iPad Pro 3 (11-inch, Cellular)
17. iPad Pro 3 (11-inch, Cellular, 1TB Model)
18. iPad Pro 3 (12.9-inch, WiFi)
19. iPad Pro 3 (12.9-inch, Cellular)
20. iPad Pro 3 (12.9-inch, Cellular, 1TB Model)
21. iPad Pro 4 (11-inch, WiFi)

iPhones 

1. iPhone 8 (Global)
2. iPhone 8 Plus (Global)
3. iPhone X (Global)
4. iPhone 8 (GSM)
5. iPhone X (GSM)
6. iPhone XS Max (China)
7. iPhone XS Max
8. iPhone XR
9. iPhone 11 Pro
10. iPhone SE (2020)
11. iPhone 6s
12. iPhone SE
13. iPhone 7 (Global)
14. iPhone 7 (GSM) 
15. iPhone 7 Plus (GSM)