I found that the actions weren't happening in Civirules and on investigation I found that all the conditions and actions were no longer there. I'm assuming that this happened during an upgrade where I went from CiviCRM 4.7 to 5.11.0 and also upgraded Civirules 2.1 to 2.5 at the same time. Maybe the problem was that I just installed the new version of Civirules rather than installing the old version on the upgraded site and and then upgrading. Things have obviously changed (for the better).
I couldn't find any release notes for new versions of Civirules. There is a note about having to re-input conditions and actions when upgrading to 2.x but I would interpret as being when you upgrade from 1.x.
Anyway, I've sported this out by re-inputting the conditions and actions and find that some of the things that didn't work for me before now do, so it was worth the hassle. I also upgraded to 2.7 before doing this.
So only real question is where are release notes for Civirules and otherwise it is hopefully useful information for others.