Node-RED reads controller tags on a CompactLogix — program tags come back null

TS ControlsThe answer

Prefix is Program:ProgramName.TagName — colon after Program, dot before the tag. A second CIP endpoint per program is cleaner than one giant list. If External Access is None on a member of a UDT, the whole read looks null. Don't publish write-capable MQTT from that flow into the cell.