These are almost exclusively local regulations, not US national requirements, and certainly not international.
So even if there were licensing, whose jurisdiction applies? What if you have distributed software development teams?
So in one sense, it's a "solved problem", with the solution being that licensing requirements would be dramatically different based on locality, but in the sense that people want — a uniform standard for hiring software developers — it's not solved at all.
Exact same thing can be said about the hiring process in general. Taxes and employment legal contracts vary from state to state. I am sure employers would love a single contract, no matter where they hire an individual, but that is not currently the case.
The mention of contractors brings up an important point though. Many people support software developer licensing because they believe (mistakenly IMO) that it would make hiring easier, but not all software development is done by employees. In a licensed profession, you cannot legally practice the trade, not even as an entrepreneur, unless you have a license. Are we to apply this same standard to software development? Nobody can write software without a license from the state? Is that even possible? What about the people writing consumer software alone at home? Can nobody even publish a web site with HTML and JavaScript without a license? A web site is essentially all you need to create a billion dollar business, so either licensing prevents that from happening, or licensing won't really be a uniform standard for the software industry.
Mark Zuckerberg was a college dropout. Thus, he wouldn't have a license. No Facebook. Maybe you're ok with that, if you hate Facebook, but nobody really thinks the problem with Facebook is that Zuck was an incompetent programmer. In any case, software development licensing would put up a major barrier to entrepreneurship in the tech industry.