When I have changed mat/photo I always get wrong list on the first print
All I do is go into the R2400 setup from photoshop print preview and click OK for any of the the settings. I then get a message that says the paper is not available - going back into setup then shows the correct list of papers.
It looks to me that Epson have done a poor job of writing the drivers and only check which carts are in on exit of setup and not on entry!
I doubt that they will fix it in the short term as good support seems to be a long way down thier list of priorities