@Franz99 

Try connect it to a pc and see if you can find it in the deivce manager as a RNDIS network adapter.

In case of the mifi in off charge mode, you can open a cmd and input “ipconfig” to see if there is any disconnected network adapter.

  @Franz99 

have you removed the battery after the update? if not, you can have a try and resinstall it, then see what happens.

can you name which  led indicator blink? and under what circumstances？

  @cloudwalker 

I cannot detect the mifi in tthe device manager. I checked the network adapter and USB controllers. The chime sound (notification sound) on my pc continuosly plays. The mifi led indicaor blinks then the pc plays the chime sounds. The chime sounds indicate that the PC can detect the mifi but is disconnected from it. The mifi device could be turning on and off as indicated by the blinking light on the led indicators. Thus, the continuous chime sound of the PC.

in the commnand prompt IP config command, under ethernet adapter it says media disconnected. So the mifi is not detected.

  @cloudwalker 

I cannot detect the SSID of the mifi, so i cannot accessed the device thru the tpmifi app or thru the tplinkmifi.net.  Theres no way (both thru wireless and USB) that I can accessed the mifi  and reinstall the firmware

When powered on, The led indicators (wifi, internet, and battery) are on steady light and will blink together very 3 seconds.

If you connect the mifi to the power brick, the led indicators will stay on and blink every 3 secs even if you power off the device.

  @Franz99 

May I ask your location(country), pls？

  @cloudwalker 

Philippines

  @Marvin_S 

It was purchased about 2 years ago. It is out of warranty. I hope there's a warranty considering that this is due to a defective firmware update in your website. There should be a guarantee for firmware updates in your website. Tp link should provide any assistance possible (sale of discounted product, repair, or recommend a third party repair). I already implored the technical support for any remedy they can provide. But they don't do repairs in my country. I don't want my device to go to waste just because of a firmware update.