We have a single server SP 2013 install that has worked fine up until possibly a month ago (MSP and client is just now reporting it). Basically they have 6 different subsites that they access via links from the main page. All of the subsites open except 1. This subsite opens to a 404 Not Found error. If I navigate to the subsite with file explorer, everything is there. When I click the subsite from the main page, the link goes to https://notrealdomain.com/Clients. I have noticed that when I click other working subsites the links all end in default.aspx and the Clients subsite does not. All data is there and I am able to access the subsite from the web using https://notrealdomain.com/Clients/SitePages/Home.aspx as a workaround, so I added a new link at the top of the main page and hid the original. Only issue is if they click the subsite on the left hand side of the main page to launch it, it redirects to the 404. Oddly enough, if I click the + next to the 404’d Clients subsite, I am able to see and access all clients under it. Any help is greatly appreciated. Thank you.