Why can't I add a custom field to the WBS Gantt columns, when I can in other projects?

Goncalo Caroco

I have a custom field that is shared by 9 projects.

However, in one of them, I can't add it to the WBS Gantt Chart columns, it doesn't even appear as an option to be added.

• Custom field is a User Picker (single user)
• Operation by non-administrators is Allowed

Goncalo Caroco

In other projects appears as it should:

The field is as follows: