You mentioned you never changed the Java setting in AMP. So Java 11 was just a visual bug. The crash report you shared clearly mentions Java 17. Also you don’t use the latest versions of their server jars. Because that would mean, you’re also on the latest minecraft version, but you’re using a very old version for minecraft 1.9.4. The latest ones would be for 1.19.4.
So, if you want to use minecraft 1.9.4 you need to change to Java 8. If you want to use minecraft 1.19.4 you need to update to the latest paper version and keep Java 17.