I've dematerialized and for some reason, I can't land, is there a way to fix this?

It should work if you wait a while and try again, sometimes this issue is caused by lag or try having a staff member force land your Tardis.

 The thing is, I'm in a personal world

you may have destroyed the demat lever so what i would do is replace it then wait a bit then try it.But I do not believe this is guaranteed