Please kindly check out if your device supports the UHD 4K.
What devices support 4K UHD?
iPhone
- Phone 7 Plus, iPhone 8 Plus, iPhone X, iPhone XR, iPhone XS, XS Max, iPhone 11, iPhone 11 Pro, iPhone 11 Pro Max, iPhone12, iPhone 12 Pro, iPhone 12 Pro Max or newer devices
iPad
- iPad Pro 10.5, iPad Pro 11, iPad Pro 12.9 (1th), iPad Pro 12.9 (2th), iPad Pro 12.9 (3th), iPad mini (5th), iPad Air (3th), iPad (7th), or newer devices
Please kindly understand that it's not available to support the 4K UHD for other devices.