Why does my Galaxy S4 not acknowledge the SIM card?

[AC Question]

why does my galaxy s4 not acknowledge the SIM card?

It's very frustrating!! For a long while now (I don't know exactly how long, but upwards of 6 months) my phone would randomly pop up a message that said "ER no SIM inserted" with a button that said restart, and that was the only thing you could do. Usually that would fix it for a bit. But it would always come back and more and more frequently. Really annoying.
I sent my phone in for some repairs (replaced the screen and the led) and they also replaced the SIM card and the SIM card port. Didn't receive the message for a while but then it was back all to soon.
Now I sometimes get the message box telling me to restart the phone, but what usually happens now is I just get an icon in the notification panel of a SIM card with an x on it and it says "No SIM inserted. Insert SIM card." So I'll restart the phone and that didn't do anything, I'll take out the battery and take out the SIM card, leave it all out for a minute-- in case it needed to cool down or anything-- put it all back in and maybe it fixes it for a little while. But I haven't had it work like a phone for the past 48 hours straight.
Would testing it to the factory settings fix it?
I've also tried altering the mobile connection settings to GSM only.

 

[B. Diddy]

Re: why does my galaxy s4 not acknowledge the SIM card?

Welcome to Android Central! Who did the repair? I'd contact them and let them know about the persistent issue. Maybe their SIM reader repair wasn't up to snuff. Also, are you sure they replaced the SIM card itself? SIM cards are provided by the carrier, so if this was an independent repair shop, it would seem a little odd for them to obtain a new SIM card for you.