the query says it all... have an Adtran 550 atlas that has been up and running for quite some time
it's current firmware version is C.09.04
is there a later version available?
if so from where do I get it?
not finding anything in the support page
The last FW released for the ATLAS 550 was C.09.04, which is what you have.
It looks like the ATLAS chassis firmware has been removed from our website. I'll have to ask if it can made available again, but that decision is above my pay grade.