Welcome! This forum has a treasure trove of great info – Scouters helping Scouters! Just a heads up, though - all content, information, and opinions shared on this forum are those of the author, not the BSA.
That user should not be a Den Leader, committee member is their role.
In the Original Scout book, I go to Pack Roster, select the user. When I click to their account, I don’t see the button on the bottom right of the page to add roles, like we see on other users.
I added 2 screenshots. One for the user with the missing button and an example of what other users have.
Unless the CC is also the COR or the COR Delegate, they do not have the ability to do so.
The COR can log on to my.scouting and make the change themselves. Alternatively, if they want to delegate that responsibility to another registered leader (like the CC), the COR can log on to my.scouting and designate the one registered scouter they wish to delegate this responsibility to using the Functional Roles in the Position Manager.