Hmm. I don’t know why the browse would work but then when reading the device would return an error code instead.
If you can get a Wireshark capture from the Ignition server where you start it, then edit/save the device in the gateway, then let at least one failed read occur, that might help.
It might have something to do with CIP unconnected vs connected messaging. Browsing and that “ReadBrowseHashRequest” you’re seeing in the logs use unconnected messaging. Read and writing tag values requires using connected messaging, which requires that a logical CIP connection be established via the ForwardOpen service.
You have 3 different PLCs involved here - if any of these are unable to establish a connection to the next or have a connection opened, e.g. because it’s already got too many connections to it, that might explain what you’re seeing.
I would check this part out--all but the very latest Logix processors have strict limits on total connection counts. And chassis-based network devices (ENBT, etc) also have connection limits.
This document has more information in Chapter 3:
Logix 5580 and 5480 processors have communications coprocessors that apparently lift these limits for their built-in ports.
