Hey craigz,
it's all good, man. Hope you have been well, too!
I've tried a fresh install of the latest Unity, PlayMaker and GDE version to see if there's a problem with the GDE actions or if GDE is incompatible with later Unity versions, and noticed that I had to apply the two patches that Celeste
posted on the Unity forum regarding ExcelImporter errors and GDEArray actions not showing up in the Action Browser for everything to work.
I think the latter is the cause of your problem, in the sense that sometimes when updating PlayMaker or Unity itself it can't find find the reference to particular scripts because the GUIDs (unique identifiers stored in the .meta files) of these scripts might have changed (this can also happen to components, which leaves you with missing script references). When you open the FSM described in these errors, you will see empty actions where the GDEGetStringArray actions were beforehand.
So you either had to apply that
patch before updating Unity or you've already applied it before, breaking the references to certain GDEArray actions.
I hope you've made a backup of your project before updating, because otherwise you need to either manually re-add and configure any missing action (which can become quite cumbersome) or fix the GUIDs yourself as described in the guide
here (which is also a bit difficult). At the bottom of that guide it also lists what else might have caused this or rather how to prevent something like this happening in the future. I've also had to go through such problems a few times and they're no fun, but sh*t happens..
If you do have a backup, you can try to replace the GDEGetStringArray.meta file from before the update with the current one (visible in the explorer/finder when viewing hidden files is enabled) and reload the scene to see if the FSM can find the script now. It's important that you haven't saved the scene after the update though, as it also saves these missing-action-placeholders. You could also try to copy the scene from the backup into your active project after the patch has been applied.
When nothing helps, you can still revert back to your previous set-up, stick to it for your current project and only use a higher Unity version when starting a new one.
Hope that offers some clarity or leads on how to fix this. Good luck, though