So this one is a little strange, for me to get it to work I went into the instance list and removed all the other instances and added only my home instance sh.itjust.works. From there liftoff should be using your account on your home instance when interacting with the others. Liftoff seems setup base for users who do not have an account on any instance and therefore indexes the main popular ones for content. Removing those extra instances seems to force liftoff to interact with the fediverse through only your home instance.
Another possible reason, in general settings, if you have the setting "see all posts from everywhere" or something to that regard on, then liftoff looks at the whole fediverse and not just through your home instance. On instances that liftoff finds, some may be defederated or not indexed with your home instance therefore you cannot interact with them. I recommend just turning this setting off. If you need a more detailed breakdown let me know ๐