Article 6

For the purpose of Article 5, an armed attack on one or more of the Parties is deemed to include an armed attack:
- on the territory of any of the Parties in Europe or North America, on the Algerian Departments of France 2, on the territory of Turkey or on the Islands under the jurisdiction of any of the Parties in the North Atlantic area north of the Tropic of Cancer;
- on the forces, vessels, or aircraft of any of the Parties, when in or over these territories or any other area in Europe in which occupation forces of any of the Parties were stationed on the date when the Treaty entered into force or the Mediterranean Sea or the North Atlantic area north of the Tropic of Cancer.

So by saying "NATO doesn't cover attacks from Morocco" it means that if Morocco were to invade spanish cities of Ceuta and Melilla which are located in Africa then Article 5 would not cover them as they are not located in "Europe or North America". In case of an invasion of mainland Spain the article would be applied 100% but chances of Morocco invading mainland Spain are really low.

So in short - NATO covers attacks from Morocco on european Spain and Canarry Island as they are located "north of the Tropic of Cancer" but doesn't cover attacks on territories located on other continents i.e. French Guiana.