Samsung S4 - txt messages not showing

[mfl]

My S3 has the Navigation plus option (standard in our Oz S3) and is temperamental when it comes to showing txt messages on the screen - when it isn't working the screen shows 'no messages in inbox', but at other times it works as it should.

I have deleted the phone profile a couple of times now and re-paired the phone to the car and always give the car permission to access my phone.

Any suggestions appreciated ..