Thanks to everyone who had sent me screenshots and information on what Minecraft versions their server was running on!
When I built the first version of TokensPlus, I did not realize that there was a significant change to the ItemStack/Material logic starting with 1.13.x. Because of this, how I was constructing the items was not going to work for earlier versions of Minecraft (< 1.13.x).
With this update, I have been able to update the ItemStack/Material logic to work properly for Legacy versions of Minecraft. I tried my best to test all earlier versions (1.8.8, 1.9.4, 1.10.2, 1.11.2 and 12.2) and found that the plugin was working as intended (just as it was on the latest version of Minecraft).
Please continue to report any and all issues with the plugin and I will try my best to resolve things!