I upgraded from Windows 7 to Windows 10 over a month ago. I noticed immediately that I could not connect to certain websites, mainly https websites, such as financial sites. I never had this problem before. After researching online, I learned that I could flush the DNS cache and then connect. It would work for a few minutes and then I would have to flush the cache again. This happened for a few days and then the problem went away. It began again two days ago. I have other computers in the house running Windows 10 with no problem, so it is not a router or internal network problem. It just occurs on one machine. I have to run a Flush DNS utility several times to do banking, pay bills, etc. Very frustrating!