You really should provide more information in your request for help, such as the logs. There is item on the Settings menu to zip them for attachment to your post.
That said, the recording service is probably not running. Have you rebooted? That should start the service. Are you on Win 10? If so, you may have to make a change to the service settings to get a reliable start in system startup. You could also look at the NPVR program group in the Start menu where there should be a start or restart the recording service choice.
As background, there are two parts to NPVR: the recording service that runs in the background and manages the tuners, recordings, scheduling, etc and NPVR which provides what you see: menu, plays videos, displays live TV. They need to be able to communicate within your computer; sometimes firewalls and anti-virus gets in the way.
Yep, what he said. First thing you need to do is check your recording service is running. It looks like it hasn't started, so the frontend nextpvr.exe process is unable to connect to it.