License problem with Studio 2017 - back in trial mode

I upgraded from Studio 2015 to 2017 yesterday, after having bought the upgrade in August.

I installed Studio 2017, successfully activated the upgraded license, and started working. I did not deactivate Studio 2015 as I assumed I could run this alongside Studio 2017. Today I opened Studio 2015 to export a few settings (AutoCorrect files), and when I opened Studio 2017 it said I am using the trial version. When I try to activate it using the code I received yesterday, I get an error message saying "Activation not allowed as remaining quantity is 0".

I already logged a licensing ticket, but maybe there is a quick and easy workaround?

Maybe I have to uninstall Studio 2015? However, I can't seem to deactivate my license for that.


Edit:

I just realized that my problem is quite similar to what Emmanuelle Gilbert described earlier (Key appears activated in account ...). However, rebooting several times did not help yet.