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TauseefAliKhanB , I didn't find a solution for it. I gave up on installing Parcel Service for our application. I had a support ticket on this and didn't get a good answer on the issue either. I had a conversation with another OS client about this, and the issue was most likely because we're an on-prem customer. Because of that, the email/account that Parcel Service is reading does not sync with the email/account that we registered in OS security. It appears that for that client, they are a SaaS customer and the admin contacted their OS cloud support to sync email/account between Parcel Service and OS. I'm not quite sure about the specifics and have not investigated further.
Are you an on-prem or SaaS customer? Best of luck with your implementation.