First i am very sorry if this has been asked before… i have searched with no luck to find a solution.
I am very new to Freenas and was originaly only in for its nas capabilities, and then i found out about mineos
i told my kids they would get their own server soon bcoz it all looked so easy.
Now i am totaly lost. i have downloaded
Mojang profile 1.15.1
i made a new server, clicked 1.15.1 profile… and accepted the Eula
But the runnable Jar drop down remains empty
I followed a few YT vids so i think i have done it all right…
I would be very happy if someone could help me out 
I had this exact problem when I first set setup MineOS on my Freenas server. I pulled my hair out until I saw a picture of someone’s install (entirely different problem) but there were 3 boxes checked. I can’t remember them, and I’m not going to uninstall and re-install at this point, but I installed it again and checked those three boxes. That worked. Good luck.
Are there any errors in /var/log/mineos.log?
FreeNAS seems to often introduce problems into the webui that don’t exist anywhere else, but this issue has existed in all platforms. However, it doesn’t really exist in any modern version of the webui.
If you’re able to share your /var/log/mineos.log with me, I can both see the error causing this issue, in addition to whether or not you simply need to update the webui.
The MineOS plugin for FreeNAS isn’t maintained by me, but we may see that a simple git pull and container restart is enough to fix this.