@TP-Link - 

I will try one last time to explain the fix I suggested. Being subscribed to the thread (at the moment) I don't want, through inaction, to deprive people of fixing this thing.

 

But first, like any engineer, I know that there is rarely a single cause of a problem nor is there a single solution for it; but at least I can make my suggestion as clear as it can be. So I'm not in any way dismissing other solutions mentioned here for other causes.

 

Repeating some of what I wrote before, and adding a bit;

 

Noticing that the SIM card when in place was somewhat loose and not held firmly against its seating, I reinstalled the SIM Card with a small cutout from a discarded SIM and placed on top of the metal restraint on the SIM Card.The size of the cutout was sufficient to press on the SIM Card but not so large as to hang up on any adapter (my proof of concept approach was to use a folded-up piece of paper but the cutout was easier to use). The battery then pushed it more firmly down when I put the thing together again.

 

In doing that you have to watch the closure very carefully indeed because on my device, the metal clasp,in closing, pushed the sim card way out of position so there was no way it could make contact. So watch the SIM card and the clamp (repeat and the clamp)  until the very last moment when you can't see it anymore. DON'T BE RUSHED OR CASUAL ABOUT IT.

 

Another observation to share - I initially got these errors when I trial-ran the mifi before I went off on holiday and for that used a temporary SIM which I planned to replace later. When I'd sussed out how to work the mifi and sorted the NO SIM Card issue and had travelled I put in the local SIM (Spanish HITS)..The first time I tried the latter I got the dreaded NO SIM Card message. But then I noticed that the SIM card was a very tight fit in the adapter and used a file small file on the sides of the SIM to get a good, even slightly loose, fit so that it would not be tilted one way or the other or be held up so that good contact was not achieved. From then on it has worked with no problems, over literally dozens of on/off cycles of the mifi.

 

I'm not fully recommending (*) that you do the following, at least not in extreme, but it stands to reason that the location of the SIM Card on the mifi contacts is not that dritical; there is plenty of room for a small misllignment, but the SIM contacts MUST touch the mifi contacts. So having a slightly loose fit of the SIM card in the adapter would probably work just as well or better than trying to be painfully precise.  But remember even then to monitor the metal clasp against it pushing the whole caboodle way out of position.

 

One last thing --- you will find that having a small plastic pointer (like a small pencil-sized knitting needle) is useful to hold things in place while the clamp is closing or to check to see it the SIM card moves a tiny bit if you want to have a loose fit.

 

If anyone tries this and it works, please report it here to encourage any folks that are still stumped..

 

All the best and Merry Christmas

 

 

(*) that means that if you go too far in filing SIM Cards or whatever I don't recommend it and it's all your fault!

@Kevin_Z 

 

Hi

 

We have 6 routers MR400. This is the second router happened.

 

router was working well next day doesn't detect sim.

 

we tried all solutions didn't workout. we have sent to local dealer.

 

We moved to DLINK DWR-960 works well and faster.

 

 

I have similar issue and i have tried all troublshooting steps, however no luck. Model: Archer MR400 V4

@string 

 

Hi

 

We tried to install another sim is not detecting. and put another plastic cover for the sim and put a tape

 

Nothing is working

 

This is the second router happens

 

We have sent it to local distributor waiting for result.

 

 

There is a problem with sim slot Its manfacturing poorly made

@TP-Link 

MTN GHANA

There was no damage to the SIM card /slot 

I Noticed right after purchase

And there was no firmware upgrade done too

 

 

 

 

verizon sim dont think theres damage. also got a new cudy, same issue . first cudy, its been 65 days, had two siim cards no problem.

third one it says detached with both old and new cudy, firm ware up to date

  @TP-Link 

 

Been using it for 18 months

Carrier: Jio India

 

Tried reset, new SIM etc.

Suddenly stopped recognising sim card.

No damage to cared slot.

No Firmware upgrade.