I have WordPress+Woocommerce store setup for my website www.wayanad.net
Woocommerce signup and Checkout was working fine until I installed W3 Total cache plugin. But after installing that plugin, I noticed that the checkout was not successful using the Payumoney payment gateway. The error shown was
SyntaxError: Unexpected token < in JSON at position 0..
I thought the error was caused by W3 Total cache. But actually it wasn't. I remembered that I have disabled the option "Anyone can register" in the Settings-> General area.
I tried to make a test purchase by only enabling the Woocommerce checkout option and disabling the "Anyone can register" option. That was the culprit.
As soon as I checked Anyone can register option and making the role for new users as Customers, the error message at checkout vanished and signups were processed normally.
So if you face the same error "SyntaxError: Unexpected token < in JSON at position 0" in your woocommerce store while signing up as a new user, please check whether you have enabled 'Anyone can register' option in Settings->General area in Admin panel.
Its better to make the user role as a customer which syncs nicely with Woocommerce.
Thanks for reading!