I just set up a new hub (c-5). I updated from 2.1.8.117 to 2.3.6.136 right away. When I try to create a rule I get:
error 404 app type with namespace: hubitat and name: rule-5.1 has parent type that does not match current app if you are seeing this screen repeatedly, please visit support.hubitat
I've tried soft resets, shutting down etc. If I go back to the original version rule machine does work.
Waiting a few minutes after a reboot night help if you haven't already. Otherwise, try hitting this endpoint. You can just copy and paste it into your browser's address bar:
Worked for me! I'm on version 2.3.7.145. Edit: but only on one of my two hubs, fortunately on my prod with all the zwave devices. Did not work on my identical dev hub with no zwave devices but a full reset did.