Hello,
you may want to try reposting in the official R-Sim Forum
R-SIM & SAM SIM - GSM-Forum
The latest software for the card is 9.6.2. I believe you want to use normal GSM mode since you are using an AT&T SIM. I am using 9.6.2 on a sprint iPhone 7 plus with T-Mobile, and i am not having any issues.