Access Token Expiration

Access Token Expiration

I am using the Zoho Expense API and the OAuth 2 flow for authentication. I request an access and refresh token and after an hour passes, the access token expires. I make a POST request to /oauth/v2/token to refresh my access token, but it always comes back with:

{"error_description":"Token creation throttle limit reached. Please reuse the valid tokens you currently have."}

I'm not sure why it is being throttled as I am only making a request when necessary. Any help would be greatly appreciated. Thank you.