If your CF8 installation starts without error, but returns an error 500 stating something like...
"500 the monitoring service is not available"
...on each request, then probably your neo-monitoring.xml is corrupt. This solution did the trick for me:
-Rename or delete the corrupt {cf_dir}/lib/neo-monitoring.xml
-Restart CF
CF then creates a new neo-monitoring.xml, but totally refuses to work if this file has 0 bytes.
