No responses to the cover letters, with resume attached, that you email are a red flag. This represents a genuine crisis. It calls for a comprehensive autopsy on every aspect of your job-search process.
By doing that you will uncover what you might be doing wrong. To confirm your findings you will experiment with doing it differently. Also, you will gain insight into best practices for how to launch an efficient and effective job search.
Here are just some of the pieces of the process to investigate:
Jobs you are applying to. You may think that, after years of teaching high school English, you can be a proofreader at the local weekly newspaper. Obviously, they don't agree. You might not be presenting your credentials to match their needs. Or you may have to take a formal proofreading course online.
Resume not telling a persuasive consistent story. Resumes are not a document which records your work history and presents a laundry list of skills. It's a marketing piece which tells employers exactly the story they need to hear. You have to figure out what they need and then provide that, along with details, in a coherent fashion in the resume. Yes, you leave out details which don't align with their need.
Cover letter not detailed. If the cover letter doesn't present in detail why you are a strong candidate for the job, employers won't go on to look at your resume. The purpose of the cover letter is to overwhelm the screener with your qualifications for a particular job.
The typo. Yes, it's petty. But a typo can knock a candidate out of the box. Even if you are sending out 30 cover letters a day, you still have to proofread them.
To conduct this autopsy, you could get assistance from a friend or neighbor who is seasoned in the art and science of job-hunting.