Getting invalid request for PKCEOAuthFlow.ProcessCodeFlowAsync

Hi Greg-DB ,

   Thanks for your polite-as-always explanation. 🙂 That wasn't clear to me from the doco that the authorisation URL is different every time (since it's always been the same with non-PKCE), so might be worth highlighting that in the doco for others like me who are converting.

   I got it working now with an access token (wanted to try that first so that I can test my code handles it properly when it expires), but I did try to save a refresh token at the same time, as that's what I'll use later, and various info was telling me I would get one with a code authorisation flow, but I didn't get a refresh token, only the access token.  Is there another parameter or something I need to specify, because I thought I'd done everything I needed to get the refresh token too (for offline processing).

This is what I have so far...

```

PKCEOAuthFlow=new PKCEOAuthFlow();
AuthorisationURLText=PKCEOAuthFlow.GetAuthorizeUri(OAuthResponseType.Code,APIKEY).ToString(); (plus an option to copy this to the clipboard)

OAuth2Response dxResponse=await PKCEOAuthFlow.ProcessCodeFlowAsync(code,APIKEY);
DxAccessToken=dxResponse.AccessToken;
Trace.Write($"********************************** DxAccessToken is {DxAccessToken}\r\n");
if (dxResponse.ExpiresAt is DateTime) {
    DxAccessTokenExpiry=(DateTime)dxResponse.ExpiresAt;
} else {
    DxAccessTokenExpiry=DateTime.Now;
    }
Trace.Write($"********************************** DxAccessTokenExpiry is {DxAccessTokenExpiry}\r\n");
DxRefreshToken=dxResponse.RefreshToken;
Trace.Write($"********************************** DxRefreshToken is {DxRefreshToken}\r\n");
Authorised=true;

```

But as I said, the refresh token came up blank.

thanks,

  Donald.