Instances can go down, disappear or be unresponsive due to many reasons.
Go to your account settings now and export your account settings!
This file contains your subscriptions, follows, profile settings etc. It’s very easy to start over on a new instance when you have your export file.
Back it up, export it, save it, repeat occasionally.
One of the most surprising things about developing for the fediverse is different social media users use social media very differently.