When I try to Restart my plan I get "Failed Application processing error". It does not let me, even though I have money in the Account Balance to do so.
Their website is horrible....every time I try to restart it doesn't work, just like you. I don't know if maybe someone has posted more somewhere else but keep trying it, it will work at some point. Lately I am finding that if I enter my credit card I have saved, if I click add to new card and just re-enter my same card, it will work! It's a hassle...but works. Hope that helps. (Edit: Just realized you are trying with money in your account already. It's the same issue really, the website sucks. Keep trying. Try on a computer if you can. I have tried everything and eventually something will work lol. I don't bother calling customer service, but if you don't mind that, maybe it will work better.)