Flashing question mark folder after HDD replacement

[ilikecorn500]

I have a 20" early 2009 iMac and I replaced the hard drive because I needed more internal storage. Before I did the replacement, I used Carbon Copy Cloner to clone my old drive to the new one. After I replaced the drive, when I boot up the iMac, it just shows the flashing question mark folder. Holding down option doesn't bring up the startup manager either. I'm certain the hard drive is plugged in correctly, but this is my first Intel iMac repair so maybe I've messed something up.

I'd like to run through some solutions that don't involve re-opening the computer first. Any help is appreciated. Thanks.

 

[ilikecorn500]

Quick update:

I booted from the old drive (plugged in via USB) and I'm now going to reformat the new internal drive, and clone the old to the new again.

My keyboard wasn't plugged in directly to the Mac, which is why it wouldn't open the startup manager before.