When credit card information is entered within your MassageBook account while enrolling a client into a membership, the information is stored within your Square or MassageBook Pay account.
If you have active memberships in your MassageBook account and disconnect from Square or MassageBook Pay, no changes will occur to the memberships at that time as they will all remain active. However, if you do not reconnect to the same Square or MassageBook account before a membership attempts to renew, the renewal will fail as the card is no longer available to be charged.
Issues can occur though if you switch between processors while you have memberships active. For example, if you are connected to MassageBook Pay, enter all your membership information, then disconnect from MassageBook Pay and connect to Square, your MassageBook memberships will no longer have access to that credit card information and renewals will fail. The client's card information will need to be re-entered so it saves within the new processor.