Top Sites do not update.

My Safari, Version 12.1.1 (14607.2.6.1.1), has stopped updating my Top Sites. One website that I visit often does not appear in Top Sites. I wish it did.

I removed four of the Top Sites that appeared in the lower right corner of the Top Sites window. I removed them because I do not visit those websites as often and I was hoping that my more frequently visited websites would appear there. But Safari is continuing to show only blank space where those now-deleted Top Sites had been.

Yesterday I moved my TopSites.plist to the desktop before shutting down for the night. This morning, on restart, I find no change in Safari's Top Sites.

Does anyone have any other suggestions for getting Safari to update Top Sites?

TIA