License key NOT found

As the title says, I just bought the app from google store, restarted/shutdown phone several times, whenever I get inside the soundabout app, there is a brief blink (like minimizing app) then the error is posted at bottom screen "License key NOT found".
Meizu MX4
Android version: 5.1
Firmware version: 5.1.9.0A

App is nevertheless working properly, although the trial version will soon expire and won't be able to use it

Please help..

Sometimes Google Play cache gets out of sync.

You need both SoundAbout and the SoundAbout Pro Key. The SoundAbout Pro Key no longer has an icon, but some people were getting this cached on their phones.

Try clearing it out and downloading again.

We may have to clear the cache and data, and re-install.

1) Go into phone settings
2) Press on apps
3) Scroll to SoundAbout Pro, and press it.
4) Press clear cache, clear data, force stop, then Un-install

1) Go into phone settings
2) Press on apps
3) Scroll to SoundAbout, and press it.
4) Press clear cache, clear data, force stop, then Un-install

Download from Google Play again.

You can try the latest Beta version here:
https://soundabout.forumotion.com/f8-download-beta-versions

I did all the steps of your guide, but the problem still persists. I even tried that again, restarting this time between the installations, but...

Downloading and installing the beta version of both apps, couldn't fix the problem too...

Can you send a private message with your gmail account used. I will check Google Play

Unfortunately I have to wait 7 days in order to send a private message, since I am a new member.

P.S. It is not that hard to guess my gmail account...

OK,  It looks like it was cancelled on Aug 31 and re-purchased on Sept 1.

I refunded/cancelled the purchase.

If you want to try these un-install steps again and repurchase.  Something in Google Play must have gotten out of sync.

We may have to clear the cache and data, and re-install.

1) Go into phone settings
2) Press on apps
3) Scroll to SoundAbout Pro, and press it.
4) Press clear cache, clear data, force stop, then Un-install

1) Go into phone settings
2) Press on apps
3) Scroll to SoundAbout, and press it.
4) Press clear cache, clear data, force stop, then Un-install

Download from Google Play again.

You can try the latest Beta version here:
https://soundabout.forumotion.com/f8-download-beta-versions

Indeed I initiated a refund the first time after I saw that I couldn't get it to work (problem persisted from then).
After the refund, the trial date was reset, and it was repurchased. Then I wrote to this forum.

I re-repurchased it, following all the steps you told me, but again, no license key found...

Can you send me a private message or email, so that I can send you installs to test?