Unable to fetch new access token using performTokenRequest API

Hi Team,
We are exploring the AppAuth iOS library for our app, Followed the sample app shared for iOS.

We have our own eternal IDM server configuration and able to get the auth token and the access token as well for the first time, but when we try to use the below API to refresh the new tokens

• (void)performTokenRequest:(OIDTokenRequest *)request callback:(OIDTokenCallback)callback;

we are getting the below error always on subsequent above API usage
Error Domain=org.openid.appauth.oauth_token Code=-10 "invalid_grant: Authorization code is invalid or expired." UserInfo={OIDOAuthErrorResponseErrorKey={
}, NSLocalizedDescription=invalid_grant: Authorization code is invalid or expired., NSUnderlyingError=0x28391eaf0 {Error Domain=org.openid.appauth.remote-http Code=400 "{"error_description":"Authorization code is invalid or expired.","error":"invalid_grant"}" UserInfo={NSLocalizedDescription={"error_description":"Authorization code is invalid or expired.","error":"invalid_grant"}}}}

Start with the performTokenRequest:callback: API and the OIDTokenRequest construction used after the initial authorization, then compare it with the sample app's token flow. Check the provider configuration and returned token data to determine why a later request is treated as an expired authorization code. Done means subsequent token requests obtain a new access token without invalid_grant.