"This type of organization does not support developer mode" error

I have created a sub-organization and have invited a user to this organization, whom I want to be the developer for that organization.

He is able to login and access the sub-organization. When he goes under his user profile to select the “developer mode” button, he gets this error: " This type of organization does not support developer mode"

No one else has “developer mode” selected at this time.

Please assist. Thanks.

Hello. At the moment only 1 account is allowed to be a developer in the org hierarchy.

Only one account IS currently a developer. I turned “developer mode” off in my account so that the other admin can be the developer.

Hello.
It’s about another admin account of your top level organization can be set as developer, not sub organization’s admin account.

Understood… got it working. Thanks!