Flashing means that it's not reading the bottom.
Test - With the unit on, put a small bit of water on your hand (spit works :lol: ). Rub your hand across the face of your transducer lightly so that the moisture makes contact with the face. You should feel and hear it pinging (clicking).
Yes, you have to either be in Sonar screen, or if in split screen - the sonar section has to be chosen (blue bar up top).
Without looking at your 522, it's hard to determine what you have set where.
An easy way to check the unit is to swap them out, since you said you have two of them. If the "broken" unit works in the others place, you found your culprit - the transducer.
If the transducer is working (easily checking it as I described above), but the unit is still not working, try a soft reset:
Soft Reset (Does not delete GPS Data)
1. Turn unit OFF
2. Press and hold the PAGES key
3. Press and hold the PWR key
4. Release both buttons when the USA map appears
If that doesn't get it back to normal, you can try a hard reset too, but be advised:
Hard Reset (Deletes stored GPS Data such as Waypoints and trails)
1. Turn unit OFF
2. Press and hold the ZIN&ZOUT Keys at the same time
3. Press and hold the PWR key
4. Release both buttons when the USA map appears
If the transducer is not working, it may be as simple as replacing the transducer. At this point, I don't think you should be concerned about sending the unit back in. It might be in need of a reset, or you probably have a bad transducer. Both are easy fixes.
Please let me know if I can be of further assistance. Feel free to email me with any questions.
All the best,
Glenn