Can't sign document in Edge browser - can't find an app ???

My user clicks a link in an email from a trusted employee, asking for a signature.  The link in Outlook is clicked, up pops the default browser Edge.  The user logs in using Adobe ID.  Edge then presents a dialog box saying he needs a new app???  But it has worked in the past for this user, and other users on different PCs.  Chrome/Firefox are OK.  Screenshot attached.  It has worked before.  I have cleared caches, makes no difference.  Any ideas anyone?  Thanks.