I take this is a unix type OS, if so check the logs in the starter directory as one of the applications is probably failing to start fully so the start up process just hangs, if windows check the logs in the services directory.
In the log file in the linux server:
user_projects / epmsystem / diagnostics / logs / starter.
it indicates that there is a problem starting the opmn server
Reboot the server and restart services EPM in order it's a solution ?
Is there any change from your end or OS admin side...better peep in logs for error.
I faced this issue once where issue get resolve by reboot but again after someday it appears back, my OS admin changed the file permission of one .ctl file on linux box (sorry can't remember the file name, but its used for network info).