I recently helped a friend through a job search, and was shocked by how much the process has changed in the past 3-4 years. Recruiters are inundated with thousands of resumes. So traditional job application practices ("Write a cover letter and email in the resume") or semi-recent practices ("Cast a wide net on Monster, Indeed, LinkedIn...) perhaps no longer have the rate of return that you're expecting.
I read through the book, "What Color is your Parachute: 2018 Edition" to better help my friend, and the book offers full sections on how to do better than just "putting your resume out there." Working personal connections, announcing employment intentions during coding meetups, writing specific emails to companies you respect (independent from whether they're currently hiring for your position) or getting even more creative with getting your info out there... all of the above are practices that might not have been necessary during your last search (they certainly weren't during mine).
Maybe I'm underestimating the massive extent of blatant ageism in the software industry, but I'm quite surprised that someone with your skill set can't yell from a crowded street corner and have six recruiters materialize. That leads me to think it's not a matter of what you're offering, but rather how you're selling.