If you are using Active Directory sync and you see this message, then one cause may be you have a required resource custom field.
If this is case, AD cannot automatically add the resource to the Enterprise Resource Pool and thus, the error occurs.
One solution is to designate a default value for this required custom field. For example, set up an "Unmapped" value so that the resource is created. Now you have a value that you can filter on to clearly see which resources require updates.
The same technique can also be used with the RBS, if you are using AD Sync and RBS based security. By default, the AD created resource will not have an RBS value. No value is evaluated as the top of the RBS chain so no value filtering occurs by default. If you have a default value of "Unmapped", the resource doesn't see anything until the Administrator updates their value.
To set a custom field default value,
- Log into Project Web App as the Administrator
- Go to Server Settings
- Select Enterprise Custom Fields and Lookup Tables
- Select the custom field that is required
- Under the Lookup Table section, check the box that reads Choose a value to use as a default when adding new items.
- Select the default value using the ellipsis button.
- Select Save to update the field
- Re-run AD Sync.