Why Aren’t Employers Responding to My Applications?

Is your resume read by the right person? You need to have someone walk in your resume to the hiring manager, ideally by a former client or colleague who can vouch for your skills. Having someone put your resume at the top of the pile can be helpful. Applying online is a crap shoot.
Is your resume tailored to the job? Do not list everything you do in the order you do it, but instead highlight the relevant skills and industries.
Can the reader of your resume get a sense of your skills and experience in a matter of seconds? Keep your resume short and to the point. The theme/narrative of your career should be clear upon skimming (e.g., you studied X at college, went to law school, trained at a good firm ideally incorporating X, went in-house to a firm client, and now you want to focus on X again).
Do you stand out? Your resume and cover letter should make clear your competitive advantage.
Consider the time of year. During the summer, Thanksgiving and winter holidays, expect things to grind to a halt.