The developer has let us down - what to do now?

I have to approach the license partner, since the contract was concluded with them.

Exactly. That is my main criticism of the majority of such "big name" alliances: that often a smaller operator (with a weak balance sheet) is the actual contractual partner behind it instead of having gone directly to "sole proprietorship and son."

I will simply use "property developer/general contractor" for you from now on. Of course, in this case it was a general contractor. However, in our case it was a property developer.

Well then, I will probably also write "if or in case" for you from now on.