For a sudden, dramatic "no longer works" starter problem like this, I'd bet the terminal post connection to the field coils has come unsoldered or shorted out. That would produce a no-electricity to the armature issue, as you are experiencing. Take it to a local mom and pop small motor/electrical repair shop and pay them $5.00 to troubleshoot the starter. They can tell you instantly if my hunch is correct. 'Sure would be cheaper and less hassle for everyone from Eckler's to you just to have a simple problem like this fixed on your end and then be re-imbursed by Eckler. They won't want the darned thing shipped back to them just to resolder the connection! Ask them if they'd go for that. If it turns out to be something more serious inside (but without smoke or that telltale electrical fried smell???), THEN you can invoke the full warranty clause and send the starter back to them. The shipping company will LOVE another two-way shipment of a heavy item like a starter. They're the only ones who will win.
Marshall