Q: How do I fix this error- Some of the purchased items on this iPhone could not be transferred to your library because you are not authorized on this computer-when I am authorized?

I have made purchases on one computer (PC) that for whatever reason have NOT transferred over to my new computer. So I recently transferred all my new purchases to my old computer/library and uploaded all my songs again to my iPhone. I now have all my purchases on my phone but they won't transfer to my new computer, there are about 100 songs. I keep getting the same error notice telling me to Authorize my computer, which I have done. I even went as far as to remove all devices I have authorized and re-authorized my current computer, which is a Mac.