Rokinon E mount auto focus lens.?
 

So shoot me if this is a dumb question. I did a search and for the life of me can't understand why my Rokinon 50mm F1.4 e mount autofocus lens works fine on my A7iii and A6400 but not on my FS5ii. What am I missing here please?
The stock zoom auto focus works, my 28-135 cine zoom works...
Thanks for any enlightenment that may come this way.
Oh, and Rokinon could not answer the question but just wanted me to ship my lens to NYC for service. I should also mention that I thought perhaps the firmware on the lens was out of date so I bought a lens station and made sure it was at the latest version. Can't understand why Rokinon/Sam Yang would not have a Canadian office and service centre. But now that I know that I would never buy one of their lenses again and will probably sell both the 50mm and the 14mm I now own. In the meantime I would like to use them for the project I am shooting.
Brian