Cell Card Doesn't Allow Access to Website

We send our volunteers out with laptops, printers and Internet access cards to help seniors.  For  some reason we can not get www.Medicare.gov to open on several of the laptops.  These are new HP laptops with excellent storage and speed.  We can access other Internet sites on these laptops - google, yahoo, Social Security - but not medicare.gov.  We checked all the simple stuff - the medicare.gov site is not blocked, it isn't too large.  Any thoughts?  This has us stumped.  Using the the same Internet phone card we can access Medicare.gov on one of four Dell laptops. 

That is extremely weird, though the fact that you can do it on Dells with the same card tells me it might be a software issue on the HPs. Try running a tracert to www.medicare.gov and see where the route dies, and check your firewall policies and hosts file and make sure www.medicare.gov isn't being blocked anywhere (who knows, maybe Microsoft and/or HP has a vendetta against seniors?)

Are you using the same web browser an OS on all the laptops? I found this link that has a list of requirements for the site.  It seems a bit dated, but has a list of things to check

https://myportal.medicare.gov/eservice_enu/help/CMS-MBP_Browser_Help.html#browserrequirements

JavaScript and add blocker are two things that might be causing an issue.