Integrate one Study in another

I am trying to solve a study with a fluid flow problem and an electrochemistry problem. Both studies can be solved by themselves but if I want to solve them together or use the Velocity field of the fluid flow problem in the Electrochemistry problem it doesn't work.
The electrochemistry simulation works if I use a velocity field of (0,v) for the Electrolyte flow in the two "Tertiary Current Distribution, Nernst-Planck" options and the Brinkmann equation works if I do it seperatly.
Now I want to set as Velocity field in the two "Tertiary Current Distribution, Nernst-Planck" the solution from the brinkmann equation (br/fmp1). I solved this in a seperate studie "Study 2". but as a result of "Study 1" the error:

"Failed to find a solution.
Maximum number of Newton iterations reached.
Returned solution is not converged."

shows up.

Perhaps I make a mistake with the integration of the results of Study2 in study 1?
Can someone help me with this problem?

Thank you!
Michael