That error does not mean the artifact mod is not active, you would need to link a clip or describe exactly what you're using / shooting for any help with that. The 'requirements not met' error has 2 meanings: First: you are not allowed to refund that artifact mod because it would bring you below the minimum active mods for a column you have a mod active in, ie you have a mod active in column 5 but only have 10 active in 1-4, you cannot refund any mods in columns 1-4 due to the 10 cost requirement. Second: you're trying to activate a mod you don't have an artifact unlock available for.