Humminbird Solix Gen 2's will not recignize software update. Gen 3 did.

[Enduro67]

Hello:

I have a network with 4 Solix's. (originally all were Gen 2 MSI+ and I updated software on them to 4.020 last year)

I recently bought a Gen 3 MSI+ with software 4.070 new out of the box.

I replaced one of the Gen 2's with the Gen 3.

Last night I Tried updating the software of all 4 units to the new 4.13 revision.
I used a 16gig SD card and downloaded from humminbird website.

I updated the Gen 3 first and it worked fine.

I then tried the Gen 2's and none of them recognized a available update from the SD card.
I even tried a different SD card.

Do the Gen 2's not use the same software as the Gen 3?