Q: My pinned tabs disappeared in Sierra

I have had more than 15 pinned tabs in Safari under El Capitan for months. I am not exactly sure when they disappeared but I think it must have been after I installed GM Sierra. Two days ago when I wanted to pinned a tab, I discovered that the rest were gone. I am using Safari 10.0 (12602.1.50.0.10) under macOS Sierra version 10.12 (16A323). Anyone else experienced this?

Thanks

Tanoi