Hey Anna,
Here is my situation. I’m running everything on a staging site (no SSL certificate). My goal is to get familiar with the marketplace then push live once I’m comfortable.
Right now I’m testing by login (edge or firefox browser) on http (not secure) site by the my account page. (using the code you provided to redirect to the pro dashboard.)
I cannot pinpoint what is causing the user to be logged out. It only happens when uploading the main product image.
See screen shot for the error.
I really appreciate your help.