When you create your Yamdu account and wish to add another user alongside you as a company administrator, you may find that this is not possible.
The reason may be that the person you'd like to add is already the admin of another account. It is only possible to be the company administrator of one account at a time.
To solve this issue, the user in question will simply need to log into the account they are already a company administrator of and:
Go to User Settings
Click on Remove company/organization account from user account
Click Remove
After that, they can be added as a company administrator on another account.