Parts of PE-13 suddenly missing

I am using Premier Elements 13 on a 15-month-old iMac with Mac-OS Mojave 10.14.6 installed.

Last night it was all working fine.  This morning some aspects of PE are not working. For example, I cannot select or move images in the screen above the timeline.  If I click on the Applied Effects button to the right of the screen only a blank white panel appears.

There is some evidence that the computer underwent a restart during the night although I had not planned on one.  In fact, when the usual reminder appeared yesterday about updates being available, I clicked on the 'Remind me tomorrow' option.

In any case, it is now no longer practical to edit a video.  Any ideas what can have gone wrong and what I can do to remedy it?  Could Time Machine help (I've never used it before)? Should I reintall PE13 or buy an updated version?  Try anything else?  My thanks for any help you can offer.