@joshua it works.
Thank you so much for your support.

Thanks @joshua for suggestions.

PATCH https://<domain>/api/user/45e489ac-2d80-4f34-9fb7-82743ba70a0c API is giving same 403.

Tried with tenant id "x-fusionauth-tenantid: 74995927-1234-5678-9012-07b593cdcbd1" and API is giving same 403.

FYI, this put API was working in lower FusionAuth version 1.6.1 but recently I have upgraded to FusionAuth version 1.25.0. So same API giving 403 on new version.
They changed something in new version, it looks like they added some security feature on post/put/patch API. and GET API is working same as earlier.

Thanks @joshua for reply.

this GET request is returning the expected user data.

GET https://<domain>/api/user/45e489ac-2d80-4f34-9fb7-82743ba70a0c
Header: authorization : <auth_key>

but update user API with same auth_key returning 403 status.
PUT https://<domain>/api/user/45e489ac-2d80-4f34-9fb7-82743ba70a0c
Header: authorization : <auth_key>

I am not able to execute update user APIs via postman in fusionAuth, it is giving 403 every time AND get user is working fine. looks like something permission-related changes were done in the latest fusionAuth version.
In earlier version, I was able to execute update user API using the API key.
However API key which I am using is Super users API key. Attaching the API key page screenshot.
Could someone guide me, How can I execute FusionAuth update API via postman.