NoClassDefFoundError when calling /word endpoint

[WrongNicholas]

Returning a server-side error instead of the expected response.

Stack trace:
java.lang.NoClassDefFoundError: Could not initialize class play.api.libs.json.Writes$
at Main$.getWord(Main.scala:129)
at Main$.$anonfun$new$18(Main.scala:99)
at cask.router.Result$Success.map(Result.scala:21)
at cask.router.Result$Success.map(Result.scala:20)
at Main$.$anonfun$new$10(Main.scala:99)
at cask.router.EntryPoint.invoke(EntryPoint.scala:46)
at cask.router.Decorator$.$anonfun$invoke$2(Decorators.scala:58)
at cask.endpoints.WebEndpoint.wrapFunction(WebEndpoints.scala:14)
at cask.endpoints.WebEndpoint.wrapFunction$(WebEndpoints.scala:12)
at cask.endpoints.get.wrapFunction(WebEndpoints.scala:31)
at cask.router.Decorator$.invoke(Decorators.scala:52)
at cask.main.Main$DefaultHandler.handleRequest(Main.scala:99)
at io.undertow.server.Connectors.executeRootHandler(Connectors.java:360)
at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:830)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:750)