Agree appears only when your account is still in direct mode (Stripe: Direct Transaction = Customer->Client). Clicking it:

1. Switches the setting to Customer->Platform->Client (Stripe Express).
2. Clears the previously stored Stripe account ID and API keys for the main account, and for every additional kitchen location if you have more than one.
3. Reloads the page, which now shows a Connect <location> button for each kitchen location.

Because the old keys are removed, card payments will not work until you complete Express onboarding for each location. If you try to click Connect without agreeing first you get the message "Stripe: You need to agree first!".