I had some issues setting this up too. Double and triple check all the path settings for the containers, also check trailing slashes /
IIRC it took some tinkering in the advanced settings of Sonarr and Radarr for me as well to get it working properly.
For me the stack works, but only for a while. After a certain amount of time, one or more of the containers crash (Jackett, Sonarr, Radarr). No cluw why, still troubleshooting.