iMac 27" won't backup from Time Machine

Okay, fam, this one is really throwing me for a loop. I have a late-2015 27" iMac with the 2 TB fusion drive. I just wiped it after extensive troubleshooting for a freezing problem. I had an older WD external attached as my dedicated Time Machine backup drive. When I started the iMac it after wiping the drive, it doesn't see any of the backups so it will not restore from the drive. I tried to install OS 10.11 with the hope of backing up from a fresh OS (albeit old) and it won't recognize the wiped drive and let me install it there. It is a partitioned drive with Bootcamp as the other partition, but not sure how that would matter in this case. It just shows the BOOTCAMP drive and knows it can't install it there.

I was sure to back up right before I wiped the HD and when I look at the drive on my laptop, it shows all of the backups. I bought a new SSD drive to use as a new Time Machine drive but I'm not having any luck moving the Time Machine files to the new drive either. Kinda wondering where to go from here...