Users may find that although a membership is within the membership renewal window, if they are renewing in the back office and the button shows Upgrade Now, they are not able to renew the add-on if it already exists on the membership.
Renew the membership through Daily Sales if this issue occurs.
Steps to Duplicate
From Memberships, click the hyperlinked name of the Membership program
Click the Renewals tab, and ensure that the membership in question is within the Renewal window
Click the Prices tab, and ensure that the add-on in question is listed, and that the column named Can purchase multiple is set to No
Search for constituent, then click on the Memberships tab on the constituent record
Click the hyperlinked name of the membership to take you to the constituent's membership record.
Note that the add-on in question already exists in the Add-ons box on the membership record
Click Upgrade Now
Under What are they paying for?, look for the constituent's name, then Upgrade a membership
From this dropdown menu, choose Renew the (current membership)
Note that the add-on in question is greyed out, and unable to be chosen to renew with the membership