RSLogix 500 v8.10 is the minimum required for a MicroLogix 1400 Series A. If the controller in question here is physically a Series A then you should have the correct software version.
However,
If the controller in question here is physically a Series B then you will need to use RSLogix 500 v8.30 minimum.
I cannot view your .RSS file at the moment but my guess is that it's a Series B and that's why you get the "Unsupported processor" warning when trying to open it using v8.10.