Trouble upgrading OS on iMac
I have a Late 2009 iMac running Yosemite (10.10.5)
(3.06 GHz, Intel Core 2 Duo, 16GB 1067 DDR3)
I cannot upgrade iTunes and my iphone 8+ will no longer connect with iTunes + iPhoto on my iMac.
iTunes update stated OS 10.11 or later required. I tried to update to EL CAPITAN, but when I clicked on it in the app store it says "This version of OS 10.11 Cannot be installed on this computer."
When I click "Learn More" and nothing happens.
Is there any hope for my Late 2009 iMac?
Thanks