LM PayPal donation thanks page not redirecting

For some reason my Thanks page is not showing up after lm_paypal comes back from a paypal payment.

I've set lm_paypal Configuration -> LM PayPal -> LM PayPal donation thanks page -> /thanks (a page I have created myself). I also tried the default thanks page at /lm_paypal/donations_thanks and it still goes to the /donate page.

I've set paypal to Profile -> Selling Tools -> Website preferences -> Bring customers back to my website after they pay with PayPal -> Auto Return: On

After payment, I get returned to the donate URL with a bunch of info hidden in it:
http://autismtoolbox.org/donate?tx=0KK93279LA540410J&st=Completed&amt=5....{s%3a3%3a%22uid%22%3bs%3a1%3a%221%22%3b}&item_number=0&sig=XvKaVe%2bxOeXEiftSaVavbQTpXMsX26LNcipI8Sj%2b0fBXKvlrg6%2bB%2f5NKuFRrEECI4MlvGgXgk0uamfN7353%2frmkpY8w6rmbokZkvhMZ8jZ4AJhTeS7LbhPWQ%2b0kYxcbRqFS0EhTxugqPwMdbSIybyfO0aY58sOBqF3UuDaxKhAk%3d

Essentially, back to the enter your donation page.

I'm sure I'm missing something stupid - any suggestions?