I do not know much about the upper you are using, but my PSA 9mm upper the ejecter is bolted to the receiver with two bolts.. If you have the same setup, check if the ejector is connected properly, or if the ejector length is according to spec. It could also be that the ejector tip is broken or chipped.
If the brass is extracted but not ejected, the root cause could be any one of these or a combination of the following:
1. Ejector is loose
2. Ejector tip is broken
3. Ejector is out of spec.
4. Buffer spring is too heavy for the ammo you are using
5. The ammo is weak
6. The ejector gate is out of spec.