Samsung S4, new sim card (today). Error: Sim card is not readable

[AC Question]

purchased used Samsung S4, tested use. Sim card removed from seller.
sim card from S6 doesn't fit so another trip out to purchase brand new sim card. Now this sim card not readable. All of this because my troublesome S6 that heats up to burning, battery dead at 2 hours, etc etc finally died today.
So, maybe I'm crazy to stay with Samsung, but right now I"m just trying to get a working phone again. Any ideas why a new sim card won't work????

 

[B. Diddy]

Welcome to Android Central! What's the exact model number of the S4? Are you sure it's compatible with your carrier?