This morning when I started up Google Chrome and tried to log in to Gmail the page kept coming up "Gmail app unreachable". Curiously, when using Firefox Gmail loaded up fine.
I found a solution to this issue that works for me. Right-click the shortcut that you use to start Google Chrome, then on the Shortcut tab in the box marked Target which contains the full path to chrome.exe, append a space followed by --ssl-version-max=tls1 (that last character is a number 1.)
I have no idea what this does but as I say, it worked for me.