Trying to delete Active Directory but getting error's

Hi There, 

I am trying to delete an Active Directory that I have. I have removed all subscriptions from this Active Directory but now I get the message:

• Directory contains one or more applications that were added by a user or administrator.

Under the Active Directory, I have no applications (it used to have applications and I have since removed them).

I don't have any other subscriptions tied to this Active Directory. It could have been used for an Office 365 trial quite a few years ago.

How can I remove this? Tried almost everything.

Thanks