Help - all my Chart Config Editor saved templates have disappeared!

[ruthc]

I have spent the last 2 days meticulously creating and saving Chart Config Editor templates  for my developers to use (I LOVE this feature). However, they all disappeared at about 4pm GTM on 13th May, and I cannot access them anymore!

I have tested creating a new one. I get a message saying that the template has been saved, but I cannot see it in the saved templates - I get the same message that there are no saved templates.

I am on Looker Original, version 25.6.17.