I upgraded from community edition 3.5 to 4.2.4. I can start Neo4j but cannot open the browser. I get a blank screen at HTTP://localhost:7474. Have tried uninstalling and reinstalling, checking the conf settings but no luck so far.
Is the 4.2.4 instance reading the graph that was populated from 3.5? and if so then was this database also upgraded to 4.2 format?
Also, you should find some details of failure in logs\debug.log and/or logs\neo4j.log
I have uninstalled and reinstalled so database format should not be an issue.
Could be a browser caching issue. Try opening up an incognito window (or emptying your browser cache) and hitting the url again.