Octoprint, MQTT, and JSONPATH

[vzorglub (Vincent Regaud)]

I did a quick and dirty test and it works for me:
I used exactly your item definition
and I was sending the Json via node-red through mqtt but that should not make a difference

2018-08-20 01:47:04.209 [vent.ItemStateChangedEvent] - PrusaMk3_Temperature_Tool0 changed from NULL to 24.9
2018-08-20 01:48:18.327 [vent.ItemStateChangedEvent] - PrusaMk3_Temperature_Tool0 changed from 24.9 to 24.6

Maybe a quick clearing of the cache will make it work… Maybe…

Clear the Cache

Often when one encounters a problem with OH, particularly after an update, OH will refuse to run or certain parts of OH stop working. Some reported errors include: 500 or 404 errors when accessing the UIs lots of exceptions from Jetty or other core components in openhab.log OH refuses to start at all The first step in debugging the problem is to clear the tmp and cache. Installed OH If you are running an installed OH (openHABian, installed using apt or yum): openhab-cli stop openhab-cl…