That's odd ... it works on my ipad. Are you sure you're using the 'Blackboard Mobile Learn' app?
I tried it again, it didn't work, then an update for the newer IOS version (like literally for me just) comes through, of which I update, and now it works. Weird right?
In my opinion so far, it seems better than using LMS, because firstly, it's more neat, secondly, I don't need to log in 100 times, and thirdly, it actually doesn't come up with any weird errors or things not loading. #againmarrsavestheday.
I only found out today (at about 1am or something) that you can use 'Tools' to access the grades, which is less likely to stuff up (this is for subjects like Genes and Genomes where they don't have a direct access My Grades section).