Safari no longer allows me to reopen windows from last session
I often have several tabs open in Safari while I simultaneously work on different projects. After shutting down my iMac, the tabs would automatically restore on restart. Now (since El Capitan?) it doesn't happen, and the "Restore all open windows from last session" is greyed out in the History section. I can't find anything in Preferences that would affect this. Anybody have any ideas?
Alan
iMac, Mac OS X (10.7)