Unable to run the main method - scala

Question

I am currently working on a system where staff members in an organization can be informed regarding their pending tasks to be completed by their managers via devices. This is demonstrated via the following classes:
Staff
Manager (Extends Staff)
Device (Receives tasks and removes them once completed)
Task
System (Assigns tasks)
Main
I am currently stuck at a point where I am unable to determine why I cannot run my classes, as I receive a non-zero exit code of 1.
The problem currently seems to lie within the Main.scala file, at the moment:
object Main {
def main(args: Array[String]): Unit = {
var system = new System
var s1 = new Staff(1, "John", "johndoe#outlook.com", "Brazil")
system.addStaff(s1)
var s2 = new Manager(2, "Reese", "reesecups#gmail.com", "Japan")
system.addStaff(s2)
s2.assignTask(system, 1, "PLEASE WORK")
}
}
The code used to run as intended, however when I added the following line to the Main.scala file:
s2.assignTask(system, 1, "PLEASE WORK")
I received the following error:
[error] java.lang.RuntimeException: No main class detected.
[error] at scala.sys.package$.error(package.scala:30)
[error] at sbt.Defaults$.$anonfun$bgRunTask$4(Defaults.scala:1477)
[error] at scala.Option.getOrElse(Option.scala:189)
[error] at sbt.Defaults$.$anonfun$bgRunTask$3(Defaults.scala:1477)
[error] at scala.Function1.$anonfun$compose$1(Function1.scala:49)
[error] at sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:62)
[error] at sbt.std.Transform$$anon$4.work(Transform.scala:67)
[error] at sbt.Execute.$anonfun$submit$2(Execute.scala:281)
[error] at sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:19)
[error] at sbt.Execute.work(Execute.scala:290)
[error] at sbt.Execute.$anonfun$submit$1(Execute.scala:281)
[error] at sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:178)
[error] at sbt.CompletionService$$anon$2.call(CompletionService.scala:37)
[error] at java.util.concurrent.FutureTask.run(Unknown Source)
[error] at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
[error] at java.util.concurrent.FutureTask.run(Unknown Source)
[error] at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
[error] at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
[error] at java.lang.Thread.run(Unknown Source)
[error] (Compile / bgRun) No main class detected.
Is there any indication to what the problem may be?