Temple Recommend Activation Errors

When attempting to activate a temple recommend, I get the following error message:
"A recommend book was not found for the recommend number entered"
What does this mean and how is it remedied?

Temple recommend books are issued to a specific ward. If the recommend doesn't match the ward where that member's records currently reside, that creates an issue. Likewise, if the book isn't matched to any ward.

It might be that someone failed to acknowledge the receipt of that book, or it wasn't marked when it was sent out.

I'd contact support to see if they can figure out exactly what's wrong.