We had missed it here (I've added it now), but we tend to accept has to for needs to everywhere. If you want to be precise in your translations, I think actually behöver only means needs to, and has to is only måste. But unfortunately many speakers of English seem to use those two words interchangeably, so we've decided to accept both anyway.
Ok, so does that mean that with försöker you may or may not use att but with behöver you never use att? Is there a rule for it or you just learn by experience?
I've noticed the frequency of complaints about alternate accepted answers not working increasing the past few days, so unless you had another error (e.g. I assume you didn't forget the "he" at the start), there might be some new bug abound.