Asynch Appointments synch not working between Appointments+ and Gcal

HI, Hope someone can help me with this.

I setup the Link between Appointments+ and GCal. The tutorial in the plugin was quite outdated but I think I managed to navigate my way through the Gcal setup correctly.
Appointments that come through A+ do get added correctly into Gcal.

However, If I try and block out some time in Gcal, it does not reflect or affect anything in A+

My client needs to be able to manually enter appointments into her Gcal via her phone and not get double booked through the website.

In the Google Calendar Settings of A+ i am using the (A+ <-> GCal Synch) setting works in both directions.

Any help would be appreciated.

Regards

Ad