it sounds like you already have Master Fader 3 installed on your DL1608.
It sounds like the DL1608 is letting you know that there is a Firmware Mismatch and needs to be updated, choose "YES Update".
To do this....
1. Turn OFF the power switch of the DL1608.
2. Use something like a straightened paper clip,... and gently push it into the tiny hole on the back of the DL1608, which is next to the Ethernet port,....
hold it in.... while you turn on the DL1608 power switch, continue to hold the paper clip in for about ten seconds after you turn it on.
It will take some time, so be patient. After the update is finished, turn the power of the DL1608 off, then back on.
When you recall one of your Master Fader 3 shows, everything should be fine.
Many people are confused and wonder how the DL mixer is able to update (or change) the firmware when it isn't connected to the internet.... HOW DID IT DO THAT?
When you downloaded Master Fader 3 from the App store, it also contained the firmware for that version of Master Fader and when the DL mixer is turned on and is not able to communicate with the iPad, it requests the firmware update.