Pro Sites conflict with Domain Mapping plugin

When Domain Mapping plugin is "network activated", user needs to sign-in twice in order to upgrade on the Pro Sites plan while he/she is already logged-in / stayed at the WP dashboard. But when the Domain Mapping plugin is NOT "network activated", when user click to upgrade from their WP admin dashboard, it brings user to the plan summary page + pricing tables without asking the second time to login on their site. Please advice.