When Dish pings your box to take a software update, you need to turn off the power (on both tuners if it is a dual tuner box). If that doesn't work try a check switch, then turn off the power. If this still doesn't work, I've found that a hard reboot (pull the plug for about 30 seconds) will do the trick.
Basically you can not get an update until it is "marked" as being available to your receiver (by model number and receiver serial number). After that you should get it. Sometimes a new upgrade is not sent out to all receivers when it is first spooled. In those cases you just have to wait.