After changing the permissions, you will likely need to restart the Health Service, and then the F5 Monitoring Service. While the Health Service is restarting, if the F5 Monitoring Service is already running, you may see temporary connection errors.
Also, can you look for any errors in the Operations Manager Event Log, specifically those that are coming from the Health Service. For the previous registry access issue, the OpsMgr log should have entries for those errors. For the current connectivity issues, it may have the same or different errors.
Thank you,
Stephen Fisher
F5 Networks