If you don't pay your eMastered subscription, your releases may be taken down from the platforms where they were distributed.
However, you'll still be able to log in to eMastered and receive any royalties you're owed.
To avoid takedowns, ensure your account always has a valid credit card. This can be done on the "Billing," section of the account page:

eMastered renews subscriptions automatically based on your signup date. If your payment fails, eMastered will notify you in advance before any music is removed.
Should a lapse occur and your music is taken down, it will be restored once you update your card details and the pending charge goes through.
You can update payment info at https://emastered.com/account/billing.