Alice Vattiato

14 days after paying my realm, the same realm expired, in that time, on the setting page says 0-day remaining. When expired I contact Mojang support, useless as usual, they didn't respond with an actual response, with a reason why all of this is happening, they just say in a nutshell "ask Microsoft for the paying stuff". I call Microsoft support for a refund for my subscription and they immediately gave me, then I paid again, for a new whole month; now, the setting page of my realm says "Renew every 30 days" in the Duration section. 

Try to ask for a refund and purchase again if you don't see "Renew every 30 days" in the Duration section.

@Daniel Udy

Mine say 0 day remaining, but on the Windows Page for the Subscription says when the next renew will happen.

Fixed in Bedrock 1.16.1. They added the subscription on the Windows Store, with next automatic renew.