Hello,
Thank you for contacting the support.
We have merged your accounts as requested.
Please check on your end if everything is working as expected.
Please go through this video tutorial that shows you how to get started with your PRO license:
Steps to be followed:
1. Ensure that you are logged in to your paid account
https://rankmath.com/my-account/edit-account/

2. Disconnect and reconnect your account from inside WordPress:

WordPress Dashboard > Rank Math > Dashboard > Help and click the connect/disconnect and then the connect button.
You will be taken to RankMath.com again where you can connect your account to activate your license.
You do not need to remove the free version of the plugin. Everything will be ported over to the PRO version.
Hope this helps.
Thank you.
Guten Tag,
Danke. Jetzt funktioniert wieder alles.
Freundliche Grüße
Stefan
Hello,
We’re glad that we could address the concern.
Please feel free to get in touch if you require any further assistance.
Thank you.