There is a very similar question (Different SSL states as seen by Safari, Chrome and Firefox) but with a different failure reason so I am posting this one as I think it is slightly different debug.
I have been trying to clear various browser states. Is there somewhere else (DNS?) that I should be clearing that could be causing this?
The other interesting information is one time when I tried to check ssl.com on ssllabs.com tool, it took a very long time to succeed. Not all checks took a while.
I have also tried to clear various DNS (and socket) state in chrome via chrome://net-internals/#events but I suspect something might be to do with the network or even old libraries on old macs.
I am noticing this problem is occurring more on two older macs in particular.