Roseanne,

Please see my post from today (11/13).  This appears to have started for many people around the November 8th timeframe.  I can get the Send Message page to come up on my Chrome and Opera browsers at home, but not with Firefox version 49 or Safari (Mac OS X Sierra).  At work, Firefox version 45 and Internet Explorer both work fine for me.

I would say it's probably a browser version issue and will explore more.  Please have your folks focus on older versions of Firefox as well as Safari under the initial Mac OS X Sierra release.  Safari was working under Mac OS X Sierra until about 4 or 5 days ago.  Same with Firefox.  It was working until about 4 or 5 days ago.

This should have been fixed more quickly than this, quite honestly.  Or at least properly troubleshooted and diagnosed with an exact issue.