Wondering why Sevenrooms shows availability in scheduler but while checking in Peoplevine , the slot are not visible and throws a response?

Here are few things you can check from Sevenrooms side

Check for the Key 'Booking cut-off time' whether its is set up with some time

In this case, the scheduler is set up not to show slots prior to 2 hrs of reservation , this might be one of the reasons why the available slots won't show up in PV.