Unable to Toggle visible for custom fields in card for Board

​@Are_yaaah did you try to remove it, save the form, then place it back and turn it on? 

Hello! The blue on/off switch on the left means that the field is available on the cards.
Custom fields that you add to cards are not available on the board itself (what you see on the cards on the board columns). That's why the eye icon on the right is not available. There’s just not enough space to include more than the standard fields.

https://experienceleague.adobe.com/en/docs/workfront/using/agile/boards-in-workfront/customize-fields-on-card