It's been fun just not a whole lot of fun. I have a ZD1200 and testing two AP's an R550 and 750.
The R550 has a disconnected status and I was thinking I could upgrade the firmware. I already have done so for 1200.
Now running at 10.4. I can seem to find the correct patch to load from the 1200 to upgrade the R550.
Obviously you need supported firmware versions to get this working. To check if AP is supported, there are release notes for each ZD1200 release. Doesn't make sense to be unhappy if you try to use wrong firmware -- it shouldn't work and it for sure will not work. It is expected. So -- read release notes!