Well, they're probably ongoing challenges that any company needs to consider--and I'd argue that culture and communications can be challenges even within a company location as it scales. I'd shy away from ever saying they're "solved."
But the fact that there are successful companies with a significant percentage of remote and/or distributed workers suggests that they can be solved well enough.
There are plenty of very successful 100% remote companies, including GitLab, Zapier, Automattic (Wordpress) etc. I think it's fair to say they've solved it well enough.
Traditional office space also comes with its own fair share of challenges and problems.
But the fact that there are successful companies with a significant percentage of remote and/or distributed workers suggests that they can be solved well enough.