For some reason I can't change my Pokémon's nicknames. Sucks when I leave the mysterious Odd Eggs as Odd Egg and then hatch and can't be renamed.
I'm assuming this is what you see when you click on the notepad icon to change a nickname? If so then click above the Level 1. You have to be on PC to do this, but click Control+A (or the keyboard shortcut for "select all text" if it's different on Mac), then Backspace, then type your nickname and hit Enter. Works fine for me that way.
yeah its been glitchy for some time. Its on my list of things to get fixed though thanks for reminding me!