Nostr doesn't really have accounts. I'm guessing you mean the relay disappeared from your client.

Relays are the r in nostr(Notes and Other Stuff Transmitted by Relays). They relay your messages for you. They are your client's connection to the network. If you dont have at least one relay you will not be able to retrieve messages or send them. Most clients suggest certain relays to connect to. I'd start by adding several and also you can try different clients to see how your messages are relayed. Its early but getting better fast.