A membership with the 'pending' status has not yet started and is scheduled to start at a future date.
Edit the Start Date for a Pending Membership
To edit the start date of a pending membership:
Go to the member's profile (e.g. by searching for them).
Select the Membership tab.
For the currently pending membership, find the Start Date and select the three dots next to it.
To start the membership immediately, leave the selection as Today and select Confirm.
To start the membership at a different date in the future, select a new date from the dropdown and then select Confirm.