SIM 1 not allowed on Galaxy S21 Ultra 5G - known issue still occuring in 2021 August

[Krisztina K]

Hello Community,

I had been happily using my new Galaxy S21 Ultra 5G smartphone with dual SIM until a software update was installed around 20th July 2021 (Android 11 with One UI 3.1).

After the software update, my mobile internet connection started to drop for a few minutes at random times, then got resumed. This was already annoying, but I tried to find a solution for it and performed a "reset network settings" operation. Shortly after this the error message "SIM 1 not allowed" started to occur and the SIM card that I had been using in the SIM 1 slot did not connect to the network anymore. However, it worked in the SIM 2 slot.

I researched this error message and tried various (possible) solutions:

• contacted my network provider's technical support. They have reset my subscription and after I rebooted the phone, the mobile internet connection was stable for a few days (using SIM 2 slot). They also confirmed that the phone's IMEI is not blacklisted.
• performed a factory reset on the phone. This was just a waste of time as the software components' version did not downgrade to the version that I had when I bought the phone.
• tried to switch network modes for SIM 1 and SIM 2. At random constellations of network modes, the card in SIM 1 slot seems to connect to the network, but in reality, it is unusable because there is no actual connection to the network. When I try to trigger the automatic selection of networks, I always get this message: "error while searching for networks”.  If I am in a network mode that would allow manual selection of networks, then it cannot connect to the selected network (to none of them).
• triggered the connection to network by turning airplane mode on and off, but it does not make a difference.
• booted the phone in safe mode, still nothing works for SIM 1 slot.

Should not there be already a solution for this, Samsung? Plenty of users have been complaining about the same issue already for years and various models. It is hard to believe that there so many faulty hardware are built in to SIM 1 slot.

Now I have a brand new smartphone that should be capable of handling 2 SIM cards and I am here with only 1 SIM  slot that is functioning for now (the SIM 2 slot). Although the unstable mobile internet connection issue started to occur with it also. 

The phone has not been damaged or dropped and I bought it as universal/unlocked as a brand new one in June 2021.

Short summary:

After a sofware update in 2021 July, my mobile internet connection became unstable and temporarily terminated at random times. Shortly after resetting the network settings in hopes of fixing the issue, the phone started to display the error message "SIM 1 not allowed" and the SIM 1 slot has not been functioning ever since.

Please provide a solution for the issue if anyone had luck to resolve the "SIM 1 not allowed" error on S21.

[GoanGeek]

Was the phone purchased new ?
As in direct from carrier or samsung and not through ebay and stuff.

And /or have you changed networks?

As apparently

for the MM Sim 1 not allowed usually happens if your device was locked to a carrier before because most of the dual sim models the carrier usually lock the network on one of the slots so you will use their network.

[Krisztina K]

Yes, the phone was purchased as brand new. The SIM 1 slot hosted the SIM card that started to encounter the unstable mobile internet connection issue after being in use for 1.5 month. (Now it is in SIM 2 slot.)

None of the SIM cards can connect to the network in SIM 1 slot now.

[GoanGeek]

Sorry as I amended my answer above.
Could you say where yiu got the phone from?

With regards to my above statement if it does not apply to you .I would take it to a samsung service ce ntre and let them look at it.

Good luck.

[BandOfBrothers]

Hello @Krisztina K 

If this was my phone then I would ask the original supplier of the phone for assistance and or approach a Samsung Experience Store or Samsung Service Centre for them to take a look at what is going on with your phone.

[Krisztina K · Accepted solution]

Update: the root cause of the error message "SIM 1 not allowed" was found. 

I was told in a Samsung Service Centre that the phone's IMEI is blacklisted. I used the "Blacklist Pro" (paid) service of https://www.imei.info/phone_blacklist_check/ webpage that revealed which carrier has blacklisted my phone's IMEI. So I contacted the carrier's customer service and they told me that the phone's owner has not paid installments and as these are overdue, they blocked the IMEI.

As I bought the phone as "new", I already claimed a refund from the seller  as obviously I am not the original owner of the phone, but someone else.

Nevertheless, I'd suggest that Samsung rephrases this error message "SIM 1 not allowed" in a way that clearly tells that the issue is with the phone's IMEI as I wasted plenty of time until the real cause of the error got revealed.

Thanks for your replies!

[Members_yVUjdJt]

now I am experiencing the same, in some area the sim 1 turn into emergency mode only and it's the same network..... so I do a swap, the problem seem to be with sim 1 only and it just started for me a week ago 

[Members_DW4UPg2]

Same issue here.

Yesterday SIM1 only had the issue. The notification said MM1 SIM card not allowed. Half an hour later SIM2 did the same.
I've tried to switch SIM cards, reboot...etc. Nothing helped.
Today I found out that there is a small software upgrade, mainly some bugfixes. After the upgrade everything went fine for half a day.
Now all the same started again.

I've wiped the cache, reset factory settings, do all the general stuff. Nothing helps. If I reboot it goes well until an hour or so. But then the error comes back.

I would love to find final solution for this issue.

[Krisztina K]

Hello,

If anyone is still encountering this error message, I suggest that you have your phone's IMEI number checked as it might be blacklisted. It's the potential root cause of the error message.

I used this website for checking (see my previous comment):

https://www.imei.info/phone_blacklist_check/

There is also a "pro" service available (for 2.99 $ in these days) that reveals which carrier locked the IMEI number.

[Jeremy D]

Just had a similar circumstance. Phone was blacklisted in North America, bought in Tanzania. Seems like this prompt is a blacklist error.