I don't think I'm taken as seriously as other entrepreneurs because I'm a black woman with mental illness. How can I overcome impostor syndrome and prove to others that what I offer is valuable.
My advice is to start publishing. It won't be easy, and it's quite possible some people will continue to brush you off, but if you keep putting valuable content out there you'll find your audience (that will LOVE you).
Try Medium and LinkedIn for blogging, and YouTube for any video content.
Stick with it and good things will eventually happen. As Steve Martin would say, "be so good they can't ignore you." Best of luck to you!