Extension is not loading

[br33z3]

java.lang.ClassNotFoundException: burp.BurpExtender
	at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:433)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:586)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:519)
	at java.base/java.lang.Class.forName0(Native Method)
	at java.base/java.lang.Class.forName(Class.java:466)
	at burp.ab5.a(Unknown Source)
	at burp.ab5.<init>(Unknown Source)
	at burp.b__.a(Unknown Source)
	at burp.gly.lambda$panelLoaded$0(Unknown Source)
	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
	at java.base/java.lang.Thread.run(Thread.java:831)