Problem scenario
With your Trezor wallet, you want to send cryptocurrency. You copied and pasted an alphanumeric address (and all the letters in it were lowercase). You get the message "address is not valid" when you try to send the cryptocurrency from your device. What should you do?
Possible solution
Case sensitivity can be an issue. Can you click "Convert to checksum address"? This will make letters capitalized in the [hexadecimal] address. Now the address will work for sending using the Trezor application. (Not all the letters necessarily need to be capitalized. With Trezor, some letters in a hexadecimal address are capitalized but not others.)