Sage's Hat +1

You need the recipe item again

Make sure that the sage hat IS NOT ENHANCED YET. Meaning that still lv 1/1 sage hat. Not lv 10/10 wage hat.bcoz the requirements are 2 x lv 1 sage hat.
And dont equip at someone too.

Be sure the component aren't set as favored equipement, it block too...

Don't forget to check defensive team for guild battles, easy one to miss.

Try checking your different party set-ups. I've had this issue and checked everything but then remembered I had multiple party set-ups. Hope this helps. :)

Check also if a character has the gear favorited in the 'Unit Stats' menu (bottom left screen) This allows the unit to automatically equip a specific item when setting a formation. If a character has the gear "favorited" it won't allow you to upgrade the equipment desired. Hope this helps

Here, it is not equipped, I have checked it on every page.

If the icon E was equipped, it would be on the equipment, but it is not.

i hope they make unequip button for all used selected items

Nope.The hat still in equipped. try search it at unit one by one.