I have a SharePoint 2013 server using what I assume is standard HTTP authorization for access.
I have no problem accessing it from the server itself, as well as from various machines outside, including even from mobile Chrome browser.
Here are the "claims based" authentication settings for the web application in SharePoint Central Administration:
However, I cannot access it most of the time, I'd say 90%, from my Windows 10 machine, both through the browser and using SharePoint Designer 2013. I am trying to use both the System Account and various user accounts.
SP Designer just shows the login prompt again, while the browser just displays a generic "Unexpected error" message standard for each browser.
Checking the network
If I spy on the packets using Wireshark, I see that the server returns
401 UNAUTHORIZED. But my login credentials are 100% correct (including the domain name) and work fine on other machines. What's weird though is that I thought it's using HTTP authorization (a simple window pops up in the browser), but the response in Wireshark somehow mentions NTLM.
I don't have any special software on my machine like firewalls or anti-virus software.
If I leave the SharePoint page in the browser open overnight, and then come back and try to execute any XHTTP request to the server, the response from the server seems unusual - instead of the 401 the Network tab in Chrome's Dev Tools says it failed to load request or response data, and that the headers are "provisional", meaning that they were not even sent.
I guess this is part of the reason why browsers display an "Unexpected error" instead of clearly saying it's a 401.
I cannot find any pattern of when the login suddenly starts working from my machine. When it does, if I try logging in from another browser or from the same browser's Incognito mode, I get a 401 Unauthorized again.
IIS log entries
Here's how my access attempt looks like in the IIS log:
2016-11-25 09:56:06 192.168.1.158 GET /sites/ekyc/ - 443 - 192.168.1.37 Mozilla/5.0+(Windows+NT+10.0;+Win64;+x64)+AppleWebKit/537.36+(KHTML,+like+Gecko)+Chrome/57.0.2931.0+Safari/537.36 401 0 0 12
And this looks like my attempt to log in through SharePoint Designer:
2016-11-25 09:56:34 192.168.1.158 POST /_vti_bin/publishingservice.asmx - 80 - 192.168.1.37 Mozilla/4.0+(compatible;+MSIE+4.01;+Windows+NT;+MS+Search+6.0+Robot) 401 0 0 59
Couldn't find similar issues
When I researched the issue, many people seem to get 401 Unauthorized but they have a different scenario. For example, here - 401 unauthorized when connecting from outside - the problem was that 401 Unauthorized happened during any attempt to access the site from outside. However, I (and other users) have no problem accessing the site using other computers or phones and from any network.
Someone else was having a very similar issue - 401 Error Unauthorized when connecting to sharepoint 2013 - but didn't find a solution.