i cannot spend any books on skill of explorer and geologist?

i dont know why i am not able to spend any books on skills of my explorer and geologist... it says that you require 5 books in lower levels and i have almost 9 books .... plz help me

Have you spent the max amount of books per expert already? Geo 31 and Explorer 21

have you spent the minimum manuscripts first on the lower levels?

It's times like this that a screenshot would be helpful