Google Apps

Before investing in a I phone XR, I owned an Android device , on which I used Google pay (Gpay )

On acquiring the I phone , I downloaded the Google App and attempted to install Gpay ( the beauty of this app being you do not have to open any app or press any side buttons to make it function )

Because I have transferred my phone number to the Iphone , Google seems to think that their app is already installed and stays a shadowy blank, in fact I cannot open any Google apps

Is this common , am I expecting too much or am I doing something wrong in procedure. I have Ipay