Grey table borders in writer

I recently had light grey table cell borders in Writer (they don’t print), but I must have hit a hot key or something, because now all table cell borders in all odt documents don’t show up. The tables are still there, I can still access properties, add rows, etc. but it is hard to know where the cell borders are. Is there a global way to turn all table borders visible?
I was using 5.4 with this problem, upgraded to 6.0.6.2, still have the problem. I opened the same documents on a different computer with 5.2, and the light grey borders are present.

View → Table Boundaries.

On my Macs running macOS 10, invoking this has had no effect upon the visibility of the table boundary lines for several versions of LO. What is it supposed to do?

Try LODev 6.3.0.
Is the problem resolved for you?