So, turns lout it was the RAM again. Not faulty--just unseated. I think one of my cats jumped on the tower and it got jostled loose again. Embarrassing! I've had no problems since, so if anyone finds this on google looking for solutions, just try reseating your RAM!
I got a refurbished OptiPlex 3040 (Small Form Factor) about a day ago. On arrival, once it was hooked up, it wouldn't start. Blinking amber light (2, then 7) at every attempt. Eventually we seemed to discover what appeared to be a problem (wifi adapter plugged in too early) and tried again, and it worked! ...for a little bit. Monitor issues had us restart it and suddenly it wasn't working again. My partner eventually, after much frustration, reseated the CMOS battery and RAM. And it worked! It worked all the way through setup of Win10, as well as putting all my files on it and downloading my favorite programs and everything. It worked for hours. Everything seemed fine. I left it alone for a bit and came back to find that the monitor had no signal even after seemingly waking up the computer (light went from blinking white to solid white, fan was running). I figured it was a monitor issue and tried to fix it for a bit before reasoning that it could also be the tower. I shut it off via power button, then tried to turn it back on. Same as before. Blinking amber (2, then 7) before clicking off. I'm honestly a little at my wit's end and don't know enough about computers to really diagnose this. Do any of you think this sounds like a specific issue? Or have anything I can try before simply trying to exchange it? Did I do something wrong along the way? Any help is extremely appreciated.
Dell OptiPlex 3040 failing POST after working fine