Hello,
Could you check on the SEPM home screen Left hand side Bottom Corner;
How many clients are reportedly requires a Restart?
How many does have Antivirus Engine OFF?
How many does have Auto-Protect OFF?
How many does have Tamper Protection OFF?
How many are on Not Reporting Status?
Incase, if you have any clients, which have Antivirus Engine OFF, Auto-Protect OFF OR Tamper Protection OFF make sure you uninstall the same and reinstall them.
Incase, any machine requires a restart, please do the needful and incase, some clients are in Not Reporting status probably, these have never reported to the SEPM.
Could you check the same.??