The error is telling you exactly what's wrong. The values are being passed to the
GetSpellCooldown function do not identify a valid spell to check.
If you're calling this function yourself in a Lua code snippet, check for typos or other problems with the values you're passing it, and/or post the actual snippet.
If you're not calling it yourself, check the names or IDs you've entered for any spells anywhere, and make sure they match exactly what's shown in your spellbook.