Best answer by Tony
There could be a number of reasons why this is happening. I see you're on WiFi, does the same thing occur if you disable that and set it up using 3G/4G?
If so then try going into settings, apps & notifications, apps, tap on Google, then Storage, Manage Space then tap Clear All Data. Once you've done that go back one step then also tap Clear Cache.
Go back to the apps section and this time locate Google Play Services then do the same thing. Once that's done restart your phone and try to setup OK Google again.
Let me know if that doesn't fix it.