CANNOT CHANGE ORDER STATUS ON OpenCart 2.0.1.1

Hello all and a happy new year!!
After a purchase on OC 2.0.1.1 when I want to change the order status of purchase I get the following message:
SyntaxError: JSON.parse: unexpected end of data at line 1 column 1 of the JSON data OK

Does anyone know the Real reason behind this error in theis version of OpenCart.
Thank you...

When you visit the order page for first time after logging into admin. You shall see the add ip button in top of list.

You must click that so that your ip gets permission to edit.
If you did not get this or follow this step, then that error can come up.