When the membership buttons are completely grayed out, it means that your membership is currently in the process of renewing. During this process, you won't be able to cancel or change a membership.
If the membership renews successfully, the buttons will return to normal and the membership will continue on the account. Should a membership be unable to renew, the subscription will expire and the account will revert back to a free one. There are many reasons a membership may not be able to renew, such as an expired or cancelled credit card, or insufficient Game Card credits associated with your account.
Please note that the renewing process may take a few days so please be patient. If the process takes more than 10 days, please contact Customer Service via the support form so they can provide further assistance with this issue.
The best way to avoid this issue is to make sure your credit card information is up-to-date or you have sufficient Game Card credits.