How can i retrieve time machine back-up dates that are dimmed?

I recently reformatted my hard drive, but before doing so, I did a final backup on Time Machine. There were a lot of files on there.

So my "newly reformatted" machine (iMac 21.5" mid-2010 model) is back up and running snappy (Same OS 10.9.5,) BUT when I go into Time Machine to access some old files, I cannot get into the TimeMachine backups for dates before my computer reformat! Funny thing is, I can SEE the old dates, but they are dimmed out and I cannot click on them to open the window. If I go to the scrolling bar on the right side of TimeMachine, the bright/accessable dates are only the most recent TM back-ups from after my reformat. Again, the older backups are grayed (or in this case, just a dimmer color than the working one,) and cannot be selected.

How can I access my old TimeMachine saves?? I'm hoping it's something simple that I am failing to do here.... Any help or re-direction would really be appreciated!

Thank you SO much in advance to anyone who might help me here.