You CAN undo the process if the suspension is still pending at a future date. See Undo Suspension.
If the suspension has already occurred, you CAN'T undo the suspension process but you CAN resume the membership for the customer or you can Change Suspension for the customer.
One of the key differences between Change Suspension and Resume Membership is:
The Resume Membership option allows you to end the customer's membership suspension term today and enable the customer to check-in immediately.
As for the Change Suspension option, you can set the earliest suspension end date to today's date but the customer can only check-in on the following day.
To resume the membership for a customer, perform the following steps:
In the customer's page, select the Memberships tab.
Note the status of the membership that you wish the suspension removed or resume the membership.
Membership is in suspended status indicated by its amber Suspended status. Go to step 3.
You cannot resume the membership if the membership status is Active, Future, Expired, or Cancelled. The Resume Membership option is not available.
Select Resume Membership.
In the Resume Membership pop-up window, enter the Notes section if applicable.
Select OK to resume the membership.
A confirmation message appears at the top of the customer's page. All activities are recorded in the Timeline tab.