Error: redirect_uri_mismatch with Splunk Add-on for Box

Error: redirect_uri_mismatch

• response_type=code
• redirect_uri=
• client_id=8vkmhtff2x31zkrh24s0j2l22nig1ei9

Using redirect_uri: https://localhost:8000

Not sure what to check at this point...

Any other information I should provide?  What am I misssing?

Thanks!