When creating a Wallet Address Balance Alert, the first thing you need to do is choose the coin/token that you want to monitor.
Wallet Addresses are not standard across all cryptocurrencies. Bitcoin addresses are formatting differently than, say, Cardano addresses.
When you paste in a wallet address into Coinlytics, make sure the address is correct. Coinlytics tries to validate the address before checking the balance but sometimes it will need to actually go off to the blockchain and look for that address directly. If you see a message that says 'The address provided is invalid or is unused' - that address does not exist. You can verify this by using public block explorers to confirm the validity of an address.
If you're sure an address is valid and Coinlytics is rejecting it, please let us know.
Reminder: DO NOT USE PRIVATE KEYS here. If you don't know the difference between a private key and a public key, please STOP and consult with an expert before proceeding.