OK,I figured it out. I ran a clean install on a staging site to eliminate any possible issues from my child site or plugins. This is definitely due to differences in theme options.
Here is what needs to be done to match previous settings on the menu:
1. In Theme Options, go to Typography > Menu and set color for the “Main Menu Font”
2. In Theme Options, go to Styling > Menu and set color for “Menu hover font color”
3. This will still leave you with a transparent background if you have a light menu. Under Styling > Menu there is a premium option called “Custom menu hover background” that might solve that problem, but assuming you are sticking with the free theme, you will have to add the following custom CSS specification:
ul.nav-menu ul {background: #eee;}
(where #eee can be substituted with whatever light color is appropriate for your theme).
You might have to add an !important specification to make it work. (I didn’t test things that far — I just made the adjustments using the browser developer tools).
There is still another display issue with social media icons on home page (increased spacing) and I haven’t had time to go through my staging site whatever other layout issues have been introduced with this upgrade. I haven’t updated the theme on my live site and will have to give it all more thought before I do.