The reason that Morocco is not a member of the AU is because the organization admitted the SADR as a full member.

The AU covers the entire continent except for Morocco, which opposes the membership of Western Sahara as the Sahrawi Arab Democratic Republic. However, Morocco has a special status within the AU and benefits from the services available to all AU states from the institutions of the AU...(from article AU)

But the former king, Hassan II, did say Morocco was a tree with it's roots in Africa and it's branches in Europe. 81.243.50.114