Make sure that your Gradle is using the proper JDK.
Try running ./gradlew --version
in your project’s directory. The output should be something like this:
Gradle 7.0-rc-2
------------------------------------------------------------
Build time: 2021-04-01 21:26:39 UTC
Revision: 912a3368b654b71250dfc925a20d620393
Kotlin: 1.4.31
Groovy: 3.0.7
Ant: Apache Ant(TM) version 1.10.9 compiled on September 27 2020
JVM: 11.0.10 (Ubuntu 11.0.10+9-Ubuntu-0ubuntu1.20.10)
OS: Linux 5.11.4-051104-generic amd64
If the JVM points to version 1.8 then you should change it in settings. You can find it in Preferences → Build, Execution, Deployment → Build Tools → Gradle → *Gradle JDK.