TL;DR - Please contact your account manager (or firstname.lastname@example.org if you don't know who it is). They should have contacted you about renewing the license well ahead anyways, so it might be that you have an email from them somewhere in your mailbox.
Why is my license expiring?
There are two common cases for licenses to expire:
Reason 1: Awaiting payment
We issue licenses with limited expiration date right after the contract is signed and then issue full-length licenses after the invoice payment has been received. You can check the status of the license on your "My Account" screen in the Customer Portal. If you have sent the payment already and the license has not been updated, please contact your account manager or email@example.com.
Reason 2: DXU/Subscription licenses
Licenses allocated as part of the "unit" licenses (DXUs) are set to expire after the subscription term ends (typically 12 months). After renewing the subscription term, you will be issued a new set of license keys for the next term. You can check the term for each license (Expiration Date) in the Customer Portal. If you have sent the payment already and the license has not been updated, please contact your account manager or firstname.lastname@example.org.
What is "Maintenance end" and "Expiration date"
For perpetual licenses, maintenance end represents the term when your CloverCARE support package is active. CloverCARE entitles you to technical support and upgrades for the product and needs to be renewed annually - you'll find more in the terms of your contract. If maintenance ends for a perpetual license, you can continue using the product. You can only download product upgrades released during your active maintenance period.
For DXU/subscription licenses the CloverCARE support package is always included and last for the subscription term and renews with the license itself.