PS None of my frenetic internet-recommended fixes and efforts and reboots on 9/22, 9/23 helped, but the CMS website worked fine for me on 9/24.
PPS Problem came back Sept 30/Oct 1, then gone on October 2. Go figure.
Quick note since some others may see this sometime.
A few years ago, and again today, I'm having difficulty accessing CMS.GOV on either of my laptops, although I can access it on the same laptop if I unplug my computer's ethernet and use my phone as a hot spot. This is clearly some kind of DNS or internet protocol error.
Specific to CMS
I'm not the only person who's ever seen this. Here are two websites that specifically discuss difficulties that can come and go in reaching CMS.GOV
Could Occur with Other Websites
There's also a more general condition; you can just google ( You don't have permission to access _ on this server ) where _ is nothing - don't put anything - and you'll see many Q&A's of people tearing their hair out. (For example, one Windows trick is going to the CMD file and typing ipconfig /flushdns , which, for example, did not work for me, but gives the idea of the nerdiness of the problem.)
I did things like reset my DNS and cleared browser caches and nothing has worked yet. The same problem is on both Macs and PCs in my house, but there's no problem if using an iPhone hotspot. Rebooting did not help. Would rather not use my iPhone as a hotspot every time I need a CMS document on my laptop.
The main message is, Google shows that others have had the same problem sporadically and you're not crazy.