Flashing

ProblemFix
No serial port to pickUse Chrome or Edge, a USB data cable and another USB port. Close any other program using the port (gSender, serial monitor).
"Device not supported" / can't connectHold the BOOT button while plugging in USB to enter bootloader mode, then try again. Check you picked the right tab (controller vs pendant).
Browser calls the download dangerousFalse alarm on an unknown file. Choose Keep / Download anyway.

Network

ProblemFix
Ethernet PHY init failedMissing spi: or ethernet: section, wrong pins, or wiring.
Link up but IP 0.0.0.0, ping failsINT configured but not wired: set int_pin: NO_PIN. Or no DHCP server on that network.
Static IP: "Destination host unreachable"Board and PC are in different subnets. Use an address in your PC's subnet.
gSender: "Remote mode has been disabled"Use Config → Ethernet, not Remote Mode.
gSender: unable to connectIP/port in Config → Ethernet must match the board ($Telnet/Port, default 23). Click Apply Settings.
Board on Wi-Fi access point "FluidNC"config.yaml has no ethernet: section, or crashed 3 times in a row. Open http://192.168.0.1 and upload the right config.

Pendant

ProblemFix
$Pendant/Status says noneNo uart_channel1 section in config.yaml.
No path or wrong path on the pendantCheck the WebUI console for VizErr; rebuild with the .viz button on the file.
RX overflow / garbled messages on the pendant terminalBytes lost on the cable: use a shorter or shielded cable, or a lower baud rate (same on both ends). $Pendant/Debug shows the counters.
No job recovery on the pendantController firmware is older than the pendant's. Flash both.

Crashes

If the WebUI shows Controller restarted after a crash, press Copy details and send the text to us through the contact form.

A problem may already be fixed in a newer build: see the release notes and bug fixes, then update from the Flash Firmware page.