Hi Kirankumar,
Probably, this is because of a login `redirect_uri` that is missing in your gluu server OpenID client named as `oxTrust Admin GUI`. Did you customize any client in your gluu server?
Please check that openid client, there should be a redirect_uri which is `https://your-gluu-idp-domain/identity/authcode.htm`. If you find that this is missing then add there and update it. Hope It will work. I have attached an image file for a better understanding.
**FYI: You are using an old version of gluu server that has already met the End Of Life. Please upgrade with the latest one to get supports from us.**
Thanks,
Regards ~ Shakil