[Gelöst] credits

Background of the issue:
I am trying to share the credit I have on rvrentacampervan with mpvrentals.com. The site I need help with is versteckter Link.

Symptoms:
When I try and connect the site, I get a 'Migrate website service error: Migration code was not found' message.

Questions:
How can I share the credit between rvrentacampervan and mpvrentals.com?
What does the 'Migrate website service error: Migration code was not found' message mean?
How can I resolve the migration code issue?