Does Mozilla send an email when your account is about to expire?

Mozilla does send email warnings to those who have not logged into their Mozilla Account for two or more years. https://support.mozilla.org/en-US/kb/mozilla-account-deletion-inactivity

It is possible to use the Firefox web browsers without using a Mozilla Account. https://support.mozilla.org/en-US/kb/access-mozilla-services-firefox-account#w_what-services-can-i-use-with-a-mozilla-account

If you're not sure about your plan, you can verify the list of subscriptions when you log in to your account. If anything doesn't check out, you can contact the VPN/subscription support folks directly from there.

There have been some logon issues reported in the past day or two, so that could have been just that — a stuck login that's hopefully already resolved for you.