How to enable vertical ruler in writer

If I go to view, rulers, only the top ruler shows. No vertical ruler.

View → Rulers → Vertical ruler.

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I have selected the specified options in the diagram outlined here. The vertical ruler is still not displaying. How can I fix this? My O/S is Win 10 upgraded from 8.1. I copied the About info below from LibreWriter “About” page. I was able to see and use the vertical ruler previously. It’s disappearance happened with today’s update.

Version: (x64)
Build ID: 90f8dcf33c87b3705e78202e3df5142b201bd805
CPU threads: 4; OS: Windows 6.3; UI render: default;

After some more fiddling, the ruler finally ‘appeared’. I was unable to discover why.