Since version 1.7.0, Maven Resolver requires Java 8 to run and a brand new default sync context factory has been implemented. Both are not compatible with Maven 3.8.x anymore which still requires Java 7 to run. Maven 3.8.x will continue to use version 1.6.x which you will find here. This also means that you cannot make use of the features provided by version 1.7.0 and later. If you require the changes in this version, but must use Maven 3.8.x, you can build an adapted version of Maven from the branch maven-3.8.x-maven-resolver-1.7.x and use as if you would use Maven 4.