Curve Fitting Toolbox (Error fitting any model)

I get the error messages as shown in the image below whenever I try fitting any model to data. Please help

[John D'Errico]

Yes, but you have not shown how fit was called.

[dpb]

But it says you had too many input arguments so start there...

[Andreas Goser]

Probably best to try something like an example from the documentation. Then everybody could try reproducing it.