The availability of one of the service providers doesn't display properly

If the service provider's working hours are set 9:00 AM to 5:00 PM, it allows booking of the service. But if you set to 10:00 AM to 5:00 PM, all time slots won't be available. Service duration is 420 minutes, so 10 AM to 5 PM should be enough for providing service.
For another provider on the same site, it is working fine.