Cannot change dialogue in NPCs.

I cannot change dialogue in NPCs, even though in 1.15 - 1.16 I was. It just wont give me the keyboard to edit it. I pressed the (X) button many times, still did not work. Does anyone else have this issue? 

If you want to help, but don't know how to get the NPC use /give @p spawn_egg 1 51 

Note that this cannot be done in Java edition. 

 

Thanks if any developers fix this!