I've tried to install OE on a fresh webin install.
1 - I've installed the extension as described in the INSTALL file.
2 - I've unchecked the previous extension ezdhtml which also provides OE 4.x features for XML Block. 3 - When I edit a content with a XML Block attribute, nothing appears. I just have an "advanced" written. I've tried to clear the cache or inspect the settings but nothing happens.
You would have found the answer in the Oe 5 thread / FAQ, basiacally your css / js files are not loading, possible because of missing rewrite rules as described in INSTALL and FAQ. You can also always enable DevelopmentMode in ezoe.ini If the rewrite rule doesn't work, but the editor will be slightly slower when loading.