I think you should use the new repository (see https://developer.atlassian.com/server/framework/atlassian-sdk/working-with-maven/): https://packages.atlassian.com/maven-atlassian-all/
Unfortunately this repository is currently also not available (see Confluence 9.2 release EAP available now - #5 by VasylynaBurger). This may cause the problem: the artifact is not found because the repository is not available …