How to activate Glorious Tabard?

[Krothos]

I can't seem to activate this item in In-Play tab. What am I missing?

I've added the item under Magic and it appears under In-Play. I also have Iomedae selected as the character's deity. The checkbox under In-Play remains greyed-out and cannot be selected.

This character is a Aasimar Battle Herald 9, Bard 4, Standard Bearer Cavalier 2.