I mentioned this on Nexus for the last 2 releases of Tamriel_Data. The jar file is broken and wont work for anyone. You can't put a jar file in a jar file and expect the classes in that inner jar file to be usable as if their on the classpath.
You need to build a "shaded" jar file. You can do that with either maven or gradle. If I knew where the source code was, I'd post a PR.