Electron Wont boot up

Hi All,
I have 3 electron E series surface mount module. these modules are mounted on a custom board and none of the electron are booting up.
None of the RGB leds are blinking( not even comming on).
I checked the power supply. Its getting 5V and also producing 3.3V output. Its also producing 4.13V at LiPo pin.
The power supply is 5V@2A.
When powered up The module is consums around 0.5W.
It looks like these is no firmware/bootloader in these electron modules.
The test board doesn’t have much other then power supply and the RGB led. By any chance is it possible if these module got out without a bootloader or there is something else i need to do to make these work.
Any suggestions would be greatly appreciated.

Test pad D7 to GND. If the device is missing the bootloader D7 will be held high with a weak pull-up for JTAG/SWD.

If you had a blue LED on D7 like the Electron, it would be on, dimly.

If the problem is indeed the missing bootloader, then you’d need to flash that using SWD using a ST-LINK/v2 JTAG/SWD programmer (or similar). It needs to connect to D7, D6, 3V3, and GND.

I did connect an led as well. nothing on led. The e series has a place to put led on the module it self. so i added a 1 k resistor and an led.
I measure the voltage at D7 and its 0.286V.

In that case, the processor isn’t even booting up at all. That could be a power problem, insufficient grounds, short somewhere, damage during manufacture, unfortunately there are a lot of possible causes.

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i took off all the parts from the board expect

  1. 5V @ 2A power supply
  2. Connected one led to D7

Earlier the module was going through wave solder and oven, i though high temp might damage it. so this time i build it manually.

Is there anything else might be causing not boot-up issue.