When load management is not working but both the charger and the LMC look online, the usual cause is the link between them rather than either device. Work through this in order — the software checks are quicker than the physical ones, and they resolve most cases.
Start with the control channel, not the cable
The LMC chooses its channel automatically: if CAN is available it prefers CAN, and it falls back to LAN only when CAN has no communication. The charger only accepts load management on the channels enabled in its own settings.
That asymmetry is the single most common reason a healthy-looking site has no load management. If the LMC has switched to LAN because CAN dropped, but the charger has only CAN enabled, the charger deliberately rejects load management from LAN — and everything still shows as online.
"But it shows communication." The communication status in the portal comes from the LMC, and it tells you that there is a link, not which one. Hover over the green dot to see the channel. If it says LAN, then CAN is down — the LMC would not have fallen back otherwise.
What to check, in order
Run Health Status on the site. It flags load-management configuration issues and weak connections, which tells you whether you are looking at configuration or at connectivity.
Confirm the charger is in the LMC group. A charger that has fallen out of its group is not under load management at all. See You replaced or added a charger: re-attach it to the LMC.
Check the charger's OCPP source — LMC if the charger has no internet connection of its own, Internal if it does. A wrong source produces the same symptoms as a broken CAN link. See Charger's OCPP Source.
Compare the enabled control channels on the charger against the channel the LMC is using. Where both a CAN cable and a shared network exist, enable both on the charger so the LMC's automatic switching always lands on an accepted channel.
Only then look at the physical CAN layer, below.
Checking the CAN wiring on site
Confirm which socket the cable is in on the LMC. On the LMC there is no left and right — there is front and back, and CAN is the back-side socket. The sockets are labelled on the device. A CAN cable plugged into the LAN socket is a common and completely silent mistake.
On the charger, either socket will do. The charger has two RJ45 CAN ports and they are electrically identical, which is what allows CAN to be chained from one charger to the next. Only one socket on the charger carries Ethernet, and it is labelled.
Check the topology. CAN runs from the LMC to the first charger, out of that charger's second port to the next charger, and so on. The last charger in the chain carries the termination resistor in its free port.
Read the CAN port LEDs on the charger. One LED flashes when the LMC sends data. A second LED stays lit when communication is established. No flashing at all means either no messages are arriving from the LMC, or the wiring is wrong or missing. The LEDs are not bright — look closely.
Measure the line, if the LEDs are inconclusive. Power down all the chargers and the LMC (or measure from the LMC end with the LMC's own cable detached) and measure the resistance across the bus:
Around 60–80 Ω with everything connected and both terminations present — correct.
Around 120–140 Ω means only one termination is in the circuit.
Check the pins and the shielding. The two usual installation errors are mixed-up pins in the RJ45 connector, and no effective shielding in an electrically noisy environment. Note that shielded cable fitted with plastic connectors provides no shielding at all — metal connectors are needed for the screen to be continuous. Short runs tolerate no shielding; long runs, and runs alongside power cables, do not.
Check the cables themselves — not over-tight, not kinked, fully seated. If one particular charger drops out more often than the others, disconnecting that one from the chain is a legitimate test.
Two signals worth knowing
Charging works, smart charging does not. Immediate charging does not depend on the LMC, so a charger with a dead CAN link will still charge on demand. This regularly arrives described as a smart-charging bug when it is a communication problem.
Firmware versions look wrong in the site view. A blank or implausible firmware version is a hint that the charger is not communicating with the LMC, rather than a firmware problem to chase.
If CAN was working and then stopped
Remove the charger from the LMC group, wait a moment, then add it back. That is the first thing to try after any factory reset, firmware update or network change.
What to send us
The LMC serial number, the charger serial numbers, what Health Status reports, which control channels are enabled on the charger, and whether immediate charging works. With those five things we can usually tell you which side the fault is on without a second exchange.