Error accessing a share on a different server

I have installed a new array on one of our file servers, and our programmer is trying to get our .net application to save files to that share. 

But when we try to run the application, I'm getting:

ERROR: Access to the path '\\comboifs01\f$\RFF_Repository\F08FD8BD-FE4A-47C1-94EB-D1DF1874503D_T.pdf' is denied.

I added the IIS user into the share with full permissions (to test)

Can someone point me in a direction to resolve this problem??

Thanks! :)