The new phone was driving me mad and because the glitch was in the Google play app it was affecting other apps too. I had to get onto Samsung Tech three times to take remote control of my phone and each time they delved deeper until yesterday the problem was rectified without having to do the factory reset. I would very much recommend getting their help as I would never have worked this one out on my own as it was a glitch that occurred during the last update. Samsung Stars are a very good option if you need help and they are very friendly too.
At first it wouldn't show installed apps or updates which also affected other apps whose annual subscriptions were paid for via Google play,and then after the first try it showed them but could only update apps after uninstalling then reinstalling my Samsung account.
It's all working perfectly now,just unlucky with the glitch in the first place but I was starting to regret upgrading from the S7 edge.