Borrowed books from public library. How to return them? The option is not in black, not available. Please help, cannot borrow any other

[ealbinarrate]

I borrowed two books from my public library. Once I finished the first I tried to give it back, but the option when clicking with the right button is not available. If I do not return the book I cannot borrow any other. I tried to delete it, but doing that it didn't work. What can I do?