It seems related to this error: Confluence template plugin tutorial: 404 error
You can either:
- downgrade your JDK to a version with a minor version number < 255
- force the upgrade of ICU
- upgrade to a more recent version of Confluence, aka in pom.xml something like
<confluence.api.version>7.14.0</confluence.api.version> <confluence.runtime.version>7.14.0</confluence.runtime.version>