This was driving me nuts, my S9 Plus was working fine until about a week or so ago when I got a notification to restart it. After I restarted it, this started happening. I finally found the issue; go into settings and search "audio" and you will see a "separate sound app" setting, turn that off and your Google Play will work. I did force stop Google Play and clear the cache also, just in case. I feel like this is some recent update, I hate it when manufacturers mess with stuff that affects other apps.
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