Fixing the "SIM Card Not Found" Issue on the ThinkPad X1 Carbon EM7455 4G Modem

I got a 4G modem for my ThinkPad X1 Carbon: the EM7455.

Sure enough, it kept telling me “SIM card not found.” Not that it was completely unusable—it just had a hell of a time recognizing the SIM. At first I figured it was a firmware issue, then I wondered if the card I’d bought was an engineering sample. Later I looked around and found plenty of confused foreigners too:

https://forums.lenovo.com/t5/ThinkPad-X-Series-Laptops/X1-Carbon-5th-gen-Sierra-EM7455-WWAN-SIM-not-recognized-YET-and/m-p/4110375/highlight/true

https://forums.lenovo.com/t5/ThinkPad-X-Series-Laptops/X1-Carbon-5th-gen-Sierra-EM7455-WWAN-SIM-not-recognised/td-p/3623808

There are all sorts of threads on Lenovo’s own forums with the exact same problem: put the SIM in, and it isn’t recognized.

One guy even claimed to have found the cause:

Just as I was about to give that a shot… I saw something in the reviews of an eBay seller hawking EM7455 modems:

I tried it half-doubting… stuck a bit of tape on the back of the SIM card to shim it.

Problem solved! My 天王卡 finally works!

So a problem that plagued users worldwide for that long came down to nothing more than the ThinkPad’s own SIM tray being too loose…

Fucking stupid! I’m losing my mind!