Plugin Help PerWorldInventories Not working!!

Heyyy!
So I was just about to release my server to the public and I was doing last minute checks when I realised that PerWorldInventories was not working. There was no error message, it was just like it wasn't there. If there's an alternative or you know how to fix it, please tell me! Thanks!

 

@timtower After a couple of minutes I restarted my server again and It came up with this:
[03:09:13 ERROR]: Could not load 'plugins/perworldinventory-1.9.0.jar' in folder 'plugins'

I can now see that there is no perworldinventory folder and there is only the .jar that I dragged in there. Is there a way to fix it?

 

@timtower Where do I find that?

 

@Zombiefeaster
<ServersDirectory>/logs/latest.txt

 

@timtower

This was the only thing it said about perworldinventory in the log...

[17:46:31] [Server thread/ERROR]: Could not load 'plugins/perworldinventory-1.9.0.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.UnsupportedClassVersionError: me/gnat008/perworldinventory/PerWorldInventory : Unsupported major.minor version 52.0

 

@Zombiefeaster
The issue is that you are using an unsupported version of Java. Please update to Java 8.

 

@Zombie_Striker Thank you so much!!! It's fixed now