TestNG not run in intellij after update

After I upgrade intelij Ide, I can not run my project. this is gradle project

org.testng.TestNGException: 
Cannot find class in classpath: tests.sdg4
    at org.testng.xml.XmlClass.loadClass(XmlClass.java:75)
    at org.testng.xml.XmlClass.init(XmlClass.java:67)

I do not understand what is wrong with the updates of intelij however, in 2020.3.0 I could not run the testng.xml and now in 2020.3.1 I could not run anything. can someone advise how to teach intlij what is testng again?