Solver is NOT accurate

I have to do homework online and we get to see if our answers are correct immediately after submitting them. For all of the functions I put in to differentiate NONE of them were right, and the rest told me they were unsolvable (I DID try re-entering them several times each.) Very untrue, because in the end, I got help and got all of them right with help. I didnt even get the "premium package" to use the solver after I tried it on those functions. Dont upgrade for the solver! It is NOT accurate.

Alecbug about FX Calculus Problem Solver