Keep working the process. It sounds like you're doing all the right things with custom applications. One thing I've found helpful for getting past those initial HR filters is really dissecting the job descriptions for keywords they're looking for - and extending your professional narrative arc to the priorities, investments, values, direction, etc. as articulated by the C-suite (know your target better than any competing applicant). A tool like ApplicantPrime can help with that (free, btw), basically reverse-engineering what the company's ATS and hiring managers are likely looking for. It might help give your tailored resumes an extra edge.