The set up you have will work both tuners using 1 line on the HR24 without any issues so you can record a show and change channels.
If it is not, then go back in to your satellite set in your menu and repeat satellite setup.
Make sure it is set up on dual tuner. It may still be set up on single.
As far as the R15 goes, like stated it will not work.
To get the R15 to work properly you will need a swm multiswitch like posted.
If you want both tuners working on it, you will need to run 2 lines.
Unfortunately those switches are expensive.
You will also need to run a legacy LNB to it (the 4 line LNB).
A cheaper way to achieve this would to be to run it off a separate standard dish.
If you don't want a second dish, then you may even find that upgrading to MRV would be cheaper then multiswitch itself and you will have the cool feature of DVR sharing.