We have noticed that if you are using Safari as your browser, Billing terms do not accept. You will need to make sure the "Prevent cross-site tracking" setting is unchecked when loading the page (can be done temporarily for the onboarding only). This is due to how Shopify loads the form from our server inside their webpage by embedding it.
Below is an image on how to uncheck the setting, which lives under Safari > Preferences > Privacy > Prevent cross-site tracking. This can be re-enabled after completing the form, but we'd need it disabled in order to load the app properly. Another solution would be using Firefox or Chrome instead.