Some Rental Car Companies are nortorious in sending the miles to FF programs
It is not the airlines faults if the rental car miles not showing up because the airlines only post what they receive from partners.
In our experiences, the rental car companies, particularly Budget, Dollar and the like, are notoriously in not sending the miles earned. About 1/2 of the times such miles are no shows. I have one Budget in-town office told me they received Memo NOT to process airline miles even customers requested to add the FF account in. He added my AA account on the rental but warned me it may not show up at all. It never shows up.
Hertz and Avis seem a lot better in posting the miles.