License key isn't valid anymore? Perch Runway website

Hello,

On a newly installed perch runway website, i'm getting this: Sorry, your license key isn't valid for this domain.

So I can't log in anymore.

This summer installed, worked fine. Now it doesn't work anymore.

What can I do?

(please explain it for a graphic designer)

Thanks in advance for a quick reply.

I installed Runway_V3.1.5.

What information do you need to solve this?

We use PHP 7.0. Is migration to 7.3 necessary?

When I look into full error logfiles of the site:

Found problem. License Key was incorrect in config.php. Don't know how this could be changed automatically ...