Electron with 3rd Part Sim won't connect to the cloud

after the dim D7 issue I had to Flash the Electron with the ST Link. Now I’m not anymore able to connect the Electron to the cloud (great :-(). I made it like it is documented under https://support.particle.io/hc/en-us/articles/360039741113-3rd-party-SIM-cards. Ok while my device is running with 1.5.2 I changed particle compile electron --target 0.4.8 tinker.ino --saveTo firmware.bin to particle compile electron --target 1.5.2 tinker.ino --saveTo firmware.bin.
Now my electron is breathing fast light blue, that is meaning that he want to connect to the cloud.
That I could see earlier if I had a wrong APN. Now how to I bring this APN into the electron?
A couple of years Particle hat a nice GUI on the website to create this Firmware file. Today I have it to make by me self and it didn’t work. Why make Particle the use of 3rd part Sim cards so difficult. I’m sitting now 5h for this dam electron and it won’t connect. How get I to a working firmware.bin file. I’m not amused anymore.

If you reprogrammed your device using the ST/LINK after Dim D7 the problem is most likely that your device keys no longer match the cloud, and is unrelated to the 3rd-party SIM.

With the device in DFU mode (blinking yellow):

particle keys server
particle keys doctor

THX rickkas7,
this was the solution. Maybe you can add this on the 3rd part Sim card page as troubleshooting section. This was already my second Dim7 issue and this time it happens when the battery was connected to the electron.