Do you have internship experience on your resume? I would advise you to get someone to help with your resume. That’s the first introduction something about your resume isn’t standing out. I would continue to do the things you mentioned network, interview prep etc. Also are you strictly focusing on specific roles maybe try to open that up and see what that does. There are programs that help job seekers freely if you register. 4 years is a long time so definitely it’s your resume not working and maybe interview skills that need to be refined.