Hi - I'm definitely not an expert on this - as I'm just an "end customer trying to get my unit working".

But may I ask one favor, any change to use Deco App (iPhone or Android), while the Deco goes to "Constant Red Light mode" - and to check if any of these cases (let's say 3...5 cases in a row) - gives any warnings like "Cannot read SIM card" or equivalent?

I do have feeling that there could be two issues overlapping (of course I'm just guessing) - Deco switching back and forth between 5G and 4G and potential issues with processing the SIM card inside the unit. I have seen these two things happening timely overlapping, but are they truly interconnected, I have no idea...

  @HenrikEkman When it is "working" do you reach the "green light", I only reach "Green light" in 4G mode. 

In 5G mode, It stays in "Blue light" then turns red after a few hours, I bought a "Archer MR600 4G+", it is way more stable and it works, not at 5G speed but at least it is stable !

I think I will send it back. 

My X50 5G kept getting red lights whilst connected using 5G. I switched it to 4G and it worked perfectly for weeks without any problems.

I then set it back to 5G mode and changed the carrier from Automatic to O2.  Since then it has worked perfectly for a couple of months without problem.

Not sure why you have a drop down for Mobile ISP and Carrier, but this got mine working.

These problems may be location/carrier specific, I am with O2 in the UK. Maybe TP-Link could collect enough data to see which carriers are causing the most problems.

Mobile ISP: O2 - UK

Mobile Data: On

Data Roaming: Off

Network Mode: 5G Preferred

Band: Auto

Carrier: o2-PAYG

Yes - I try this evolving sequence as long as I can get it back: Make sure there is no PIN active on the SIM card

* In DECO app - reboot the router functionality (typically does not help)

* Power off, by removing the power adapter from the wall - and reboot it again

* If no help - power off, remove the SIM card, power on and re-insert the SIM card. Wait as long as the green light turns to red and with help of Deco App (when my mobile is connected to the WIFI the Deco create) try to see if the SIM card is read properly. It says "No SIM card" or equivalent if such thing happens. If the SIM card is not read, for sure the connection to 4G/5G does not happen

* If no help, when Deco is on, remove the SIM card. Press with a paper clip the reset button at the bottom. Wait at couple of minutes that the Deco comes back to live. Then with Deco App reinstall your router "from scratch" as at the first time. During the process, insert the SIM card again (and then it reads the SIM card finally at least with my unit). During my 5 days operating time, I can not counted all steps, but my educated guess is:

* 10 reboots via Deco App * 10 reboots by pulling the power adapted from the wall * Once or twice is has recovered by just waiting 15min * Once reinstalling from scracth * Once removing the SIM card

jcdauchy wrote

I am with "Free mobile" in france. You said you got it working and suddendly, it stopped working without any firmware upgrade ?

  @jcdauchy 

Bought unit in December, did not upgrade firmware at any time.

1) Setup from scratch, 5G enabled and working fine

2) Reboot (moved unit to another place), red light

3) Switched to 4G only mode, rebooted, working, left for a week, no problems on 4G

4) Reset unit and set it up again, 5G enabled and working fine
5) Reboot to test, red light

6) Changed carrier from Auto to O2
7) Reboot, 5G connected fine, still working after a month

My fix was step 6, changing the carrier from Auto to O2

4G always worked perfectly

Good information - I run over night that step 6) (Change carrier from "Auto" to "the carrier I have = Telia"). No issues, however I moved the Deco to a position there it seems to be more stable 5G (seen as Frequency as B3 and N28 in Deco App). These channels are very regional but my conclusion is that B3 is 4G and N28 is 5G in Finland.

In the alternative position of my router the N28 (or other 5G channels) were flipping on and off time to time. That makes me thinking that Deco is switching back and forth 4G and 5G somehow "locks the Deco in the Red light issue". And it does not recover - goes to "red light issue" and may even trigger the SIM card reading issue.

Anyways, I will test that setting from "Auto" to "Telia" - for sure. However, I just received a "debug SW" for my Deco and let the Deco Experts to monitor my device. My gut feeling is that from "Auto" to "carrier" may help but I could not verify it fully yet. And as you said, as you wrote - forcing the Deco to 4G only (green light) makes it stable.

The funny thing is that I've noticed that the LED is white/light blue when the unit is "on 5G" but also when it looses the 5G it will not easily turn into green. So you/I need the app and refresh the "location help pave" screen to see the channels that may flip between B and N. Or N-channel comes in and goes out.

If thappens, that there is no N-channel - the unit is actually in the 4G even the LED is white. I believe, at least if there is "active flipping back and forth".

These are specs I got from TP Link technical support:

Deco X50-5G Network type Compatibility:

• 5G: N1/N3/N5/N7/N8/N20/N28/N38/N40/N41/N77/N78
• 4G FDD-LTE: B1/B3/B5/B7/B8/B20/B28
• 4G TDD-LTE: B38/B40/B41/B42/B43
• 3G: B1/B5/B8

Interestingly, now I'm running the special debug SW,

If I go to the Deco App and request an update (that I won't do right now) it gives this screen below (infomation about the SW 1.1.2 that I had this issue when joining into this discussion thread).

The sceen belows says to me: Indeed, the TP Link team has been trying hard to resolve issues - and there is some issue with the SIM card. Not exactly what I reported, but sounds like there can be some more general issues with the SIM card. That may or may not be related to the red light issue. 

TP-Link Technical team - just let me know what I can do to support you! I'll be here for you!

The challenge is: I'll be leaving Saturday the location there is low 5G signal strength. And secondly these dropouts (red light issue) happens only few times in a day so it truly requires "a week" to get some true "statistics" to report or ideas for steps to reproduce the issue in the lab.