Posting a follow up since I finally figured this out and got it resolved.
So when we first got this SRX in, my techs hooked it up without an NPC/SPC. Not realizing the NPC was necessary to configure/go live, they started troubleshooting and apparently pulled out the RAM on the Routing Engine during their troubleshooting. When the SRX boots, it only shows 1GB RAM, but it actually has 2GB (2 x 1GB DIMMs). So they left one RAM stick out, thinking it was bad (it wasn't). The SYSIO-XGE will NOT go into ONLINE if there is only 1GB RAM in the RE. We went through with an identical SRX1400 and swapped every single module until we pulled the RE and realized it only had on RAM stick.
So there you have it... in case someone else comes across this in the future.