Invalid grant type during authorization with dropbox-oauth2

[TheKrominator]

I am using the passport authenticate with 'dropbox-oauth2' to get my login token and receive my Bearer. This worked fine until about midday yesterday when it started sending me this : error_description: 'code has already been used',
error: 'invalid_grant'

To get the Dropbox authorization screen, I use this :

app.get('/dropboxLogin', passport.authenticate('dropbox-oauth2'));

app.get('/auth/dropbox/callback',
passport.authenticate('dropbox-oauth2', { failureRedirect: '/', params:{'response_type':'token'} }),
function(req, res)
{
// Successful authentication, redirect home.
res.render('index', { title:'Dropbox Login', body:res});
});

Once I've received my token I run : axios({
method : 'post',
url : 'https://api.dropboxapi.com/oauth2/token',
params :
{
code : request.body.code,
grant_type : 'authorization_code',
redirect_uri : 'http://localhost:9000/callback',
client_id : '##############',
client_secret : '##############'
}
})

Thats when I get the error. 

[Greg-DB]

Dropbox OAuth 2 authorization codes can each only be used once. (You should just use the authorization code once, but you can store and re-use the resulting access token.)

The "code has already been used" error message should just indicate that the authorization code you're supplying has already been used. I just gave the flow a try and it seems to be working as expected for me.

Can you double check you're not accidentally re-using the authorization code, or perhaps accidentally issuing the /oauth2/token request more than once?

[TheKrominator]

I've learned that my router file was no longer being called. This caused my '/' command to not run and would return that strange error. Now, that I've reconnected my authorization routes, it is running correctly again.