The default admin account on Dell OpenManage Enterprise is the only account that has the “Backup Administrator” role assigned to it and is needed to perform a migration from 3.x to 4.x. If the password is lost, the documentation states there is no way to recover it. If you log in with a regular Administrator account you cannot edit the admin account in the GUI. It is however possible to reset the Dell OpenManage Enterprise admin account password via the API.
First, you’ll need to perform a GET request against the /api/AccountService/Accounts endpoint to find the ID of the admin account. The @odata.id field contains the full endpoint of the account. Yes, the URI is really in that weird format of /api/AccountService/Accounts('XXXXX'). You can make a PUT request against this endpoint and reset the password. I copied the entire body that was returned with a GET request of the account, deleted the fields not listed in the documentation, and set a password. Once that was done I was able to log in to the Dell OpenManage Enterprise admin account with the reset password.
Would it be possible to do this with Powershell using the Invoke-RestMethod cmdlet? What application did you use for the PUT command?
I usually have better luck with Invoke-WebRequest in PowerShell, but either should work. Postman works too if you want something with a GUI.