Hello Kent Man,
Thank you for posting this in the Microsoft Q&A Community.
From my understanding, your react application is requesting the wrong OpenID endpoint. Since you explained that this works with the Jwt application without issues, the main thing to check will be how you integrated your policies with your application.
When setting up the authority in your application, be sure that the tenant you added is your B2C tenant and not your Entra ID tenant name.
Follow this link to get more information about integrating your React application and Azure B2C
Let me know if further assistance is needed.
Babafemi