Unable to browse/select different internet plan due to Flex

When I click "Change Plan" in my account settings, I get the following error: 

"Looks like you'll need some extra help completing your order. Thanks for getting started! Since Flex is in your plan, the Xfinity Assistant can help complete your order online. Or, you can call 1-800-XFINITY."

I don't really want to call in just to see what options are available to me; I had no issues with this before, apparently getting Flex messed up the system?