Anvil won't rename my nametags (realm)

I keep trying to rename a name tag for my villager and I type it in fine but the arrow still has a cross on it? Won't work for any other non-armour items either.

I definitely have enough levels, I have 17.

I'm on a realm, but I don't own it, and at the mo I'm the only one online. I have a good connection, and it works on my creative testing world.

 

Worked fine when I did 2 in a different anvil without a block above it?