Time machine will not allow me to scroll through backups or restore

macOS High Sierra, Version 10.13.2, iMac (Retina 5K, 27-inch, Late 2014), Processor: iMac (Retina 5K, 27-inch, Late 2014), Memory: 8 GB 1600 MHz DDR3, Graphics: AMD Radeon R9 M290X 2 GB

Time Machine will not allow me to scroll through backups and obviously not restore. I have tried in vain with two external hard drives that I use for backups.