Here are a few things you might want to check:
Client ID and Secret: Make sure you have the correct OAuth client ID and secret from Kanbanote. Double-check for any typos or spaces.
Redirect URI: Ensure that the redirect URI you provided when setting up OAuth matches the one configured in your Kanbanote account.
Permissions: Make sure that your OAuth client has the necessary permissions to access the required resources in Kanbanote. Check if any additional scopes or permissions are needed.
Token Expiry: OAuth tokens have a limited lifespan. If your token has expired, you'll need to refresh it. Check the expiration time and implement token refreshing if necessary.
API Endpoint: Confirm that you are using the correct API endpoint for Kanbanote. Sometimes, changes in the API https://tech-stack.com/blog/what-is-an-api/ version or base URL can cause authentication issues.
Firewall/Proxy Issues: Check if there are any firewall or proxy settings blocking the OAuth connection. Ensure that your server can reach the Kanbanote OAuth server.
Error Messages: Take note of any error messages you receive during the OAuth process. They can provide valuable clues about what's going wrong.