In case of some most common problems WebHMI blinks with LEDs on front panel.
There are three such cases:
In case of any issue with SD card WebHMI three LEDs will blink slowly: ERR, WWW and VPN. Here is example:
If input power voltage is below normal operational limit four LEDs will blink fast: PWR, ERR, WWW and VPN. Here is example:
If any register can't be read over serial or Ethernet interfaces ERR led will blink. Here is example:
In this example there is no response from PLC over built-in RS-485 port. You can see TX LED blinking when request sent and no RX LED activity. This means that WebHMI does not receive any response on these requests.
If you have very short scan time and too many reading errors ERR led can light permanently w/o blinking.