passport-steam: Failed to discover OP endpoint URL

Using the recommended code

passport.use(new SteamStrategy({
    returnURL: 'http://mysite.com/auth/steam/return',
    realm: 'http://mysite.com/',
    apiKey: 'my key'
  },
etc.

app.use('/auth/steam',
  passport.authenticate('steam', { successRedirect: '/',
    failureRedirect: '/error' })
  );

app.use('/auth/steam/return',
  passport.authenticate('steam', {failureRedirect: '/404' }),
    function(req, res) {
      res.redirect('/');
    }
  );

Error: Failed to discover OP endpoint URL (message: No providers found for the given identifier)

Occasionally the site will progress past this stage however, resulting in the next error:

Failed to verify assertion (message: No OpenID provider was discovered for the asserted claimed identifier)

I tried the solution in #27 but I couldn’t get it to work. Has anyone gained any further understanding on this issue?

To add to this, this has been working in my app for 8 months or so, none of the code has been changed.