Ubuntu 20.04 shows a blue screen with “Activities” in upper left, but no icons

I installed Ubuntu 20.04 using VirtualBox on a W10 system. The install went normally, but once the desktop appeared, I found that I needed to adjust the display resolution, and fix the dtae display, as the month was showing up in Spanish. Somehow, in the process of doing this, when I restarted, the display comes up with a solid blue background, the word “Activities” in a black banner across the top, and in the upper left of the blue portion of the screen, the words “dave” (my user id) and “Trash”. If I move the cursor over the lighter blue vertical banner on the left side of the screen, icon labels (such as “Firefox web browser”, etc will display as the cursor moves over the area where the icon should be, but no icon appears. I cannot find any way to enter a terminal – for example, if I do a CTRL+ALT+T, I get a screen that asks for my password, then…nothing happens. AT this point, I may just do a complete re-installation, as I have no idea how I screwed this up, but there seems to be no recovery that I can find.