How can I solve this java.lang.NoClassDefFoundError exception

I am working with Extent reporting API but every time I run the code the following exception is thrown:

[RemoteTestNG] detected TestNG version 7.4.0
FAILED CONFIGURATION: @BeforeTest startReport
java.lang.NoClassDefFoundError: io/reactivex/rxjava3/subjects/PublishSubject
    at com.aventstack.extentreports.ReactiveSubject.<init>(ReactiveSubject.java:28)
    at com.aventstack.extentreports.AbstractProcessor.<init>(AbstractProcessor.java:22)
    at com.aventstack.extentreports.ExtentReports.<init>(ExtentReports.java:55)
    at testcases.BaseSetup.startReport(BaseSetup.java:42)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:133)
    at org.testng.internal.MethodInvocationHelper.invokeMethodConsideringTimeout(MethodInvocationHelper.java:62)
    at org.testng.internal.ConfigInvoker.invokeConfigurationMethod(ConfigInvoker.java:385)
    at org.testng.internal.ConfigInvoker.invokeConfigurations(ConfigInvoker.java:321)
    at org.testng.TestRunner.invokeTestConfigurations(TestRunner.java:637)
    at org.testng.TestRunner.beforeRun(TestRunner.java:627)
    at org.testng.TestRunner.run(TestRunner.java:589)
    at org.testng.SuiteRunner.runTest(SuiteRunner.java:377)
    at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:371)
    at org.testng.SuiteRunner.privateRun(SuiteRunner.java:332)
    at org.testng.SuiteRunner.run(SuiteRunner.java:276)
    at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:53)
    at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:96)
    at org.testng.TestNG.runSuitesSequentially(TestNG.java:1212)
    at org.testng.TestNG.runSuitesLocally(TestNG.java:1134)
    at org.testng.TestNG.runSuites(TestNG.java:1063)
    at org.testng.TestNG.run(TestNG.java:1031)
    at org.testng.remote.AbstractRemoteTestNG.run(AbstractRemoteTestNG.java:115)
    at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:251)
    at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:77)
Caused by: java.lang.ClassNotFoundException: io.reactivex.rxjava3.subjects.PublishSubject
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:582)
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
    ... 28 more

I need to fix this but I am unable to discover the cause of this error

Update the rxjava library to the latest version