Laravel redirects to the login page while kicking the user out, why?

Question

Laravel

What is:
1. An external site with a POST form that redirects to my site
2. A POST route that has a redirect like this: return redirect()->route('***');
3. Route GET ***, which displays some page

Problem:
When going from point 1., the user is thrown in this way:

Why is this happening? And how can the problem be solved?
Check for token removed if anything