There may be various reasons, including:
The spelling of the address. Make sure that the address contains all the necessary auxiliary characters, suffixes, and prefixes (dots, dashes).
Extra spaces. Make sure all address characters have been copied. Сheck there are no spaces at the beginning and end of the address.
Incorrect blockchain. Make sure that the network of the selected coin matches the network your address belongs to.
Some other issues. Feel free to contact our support team which is available 24/7 via email (email@example.com) or live chat.