Sim card

[MikeNY43]

Keep saying no sim card , i did everything and everything looks fine 

[BandOfBrothers]

Has this just started happening i.e has the phone accepted the sim card previously and worked OK @MikeNY43  ?

When you say you " did everything " what did that entail ?

Eject the sim and look to ensure no foreign debris is in the slot and gently wipe the chip on the sim card and then reinsert.

As a process of elimination can you try your sim card in another phone, and then another sim card in your phone and then see what happens.

I wish you all the best. Take care.  😎 

[Mitzzz999]

After all them checks... You may need to get a replacement SIM from your provider if the phone is fine.

[DaveMe457]

I am not hijacking your thread, but my experiences may help.

I week ago, I acquired an S21 Ultra. Updated to latest firmware and all Google and Samsung apps up to date.

Running fine with various SIM cards. I have multiple PAYG SIM cards from most of the major networks (I use them for testing purposes) and the S21U is unlocked and works fine with all of them.

Today I did a factory reset on the phone (it's for my wife) and I received an official Samsung S21U Clearview cover. Now I get the "SIM not installed" message whenever the case is fitted. I am aware the "smart" case has multiple sensors that detect its presence but something about this case is messing up reading/recognising the SIM. 

This may help the op to identify an issue and I will investigate further 

[DaveMe457]

Replying to my own message to some extent.

In my case the official Samsung cover possibly made the situation worse but was not the cause. In this instance the "No SIM card detected" was caused by the charging port or the cables attached to it. 

Not a job unless you wish to void your warranty, or you are not too confident with hardware, but I had to remove the charging port and all the attached cables. In recent years Samsung have incorporated the SIM holder and the USB port on one easy to replace daughterboard and even though I didn't need to replace the board, it was relatively simple to remove and replace. I then re-assembled everything, making sure the charging port was seated correctly and all the cables firmly attached. 
The fault has now gone.

This may help someone