No Signal, Impression with Pay-as-you-go SIM

Hi,
I bought an unlocked Impression to replace my old AT&T prepaid LG Prime that got water damaged. I bought one of the cheap AT&T prepaid phones at walmart and had my account info transferred to the new SIM card with that phone since my old SIM was un-usable. The new sim works fine in the phone that it came with, but when I put it into the Impression, it does not show any signal. It also does not display a number for the phone.
I tried a SIM from a friend who has a normal AT&T plan and it works fine, so the phone is ok.
Prepaid SIM's are both the orange ones that say 3G on them.
Ideas?
And yes I searched.
Thanks