Cannot remove the access control entry object on the object because the ACE isn't present

Question

Hello,
I am very new to using Powershell and Exchange Management Shell, and have no prior experience using either of these tools. However, the software I am installing requires me to use the EMS tool in order to set certain permissions for a user in Exchange, which
will be like the admin account. 
The command I am attempting to run follows as:
Get-ExchangeServer | Remove-ADPermission -User $newusername -Deny -ExtendedRights Receive-As -Confirm:$False 
This throws me an error saying:
cannot remove the access control entry on the object because the ACE isn't present. I've done some research, and have found that this error is quite common, but the solutions do not apply to what I am specifically trying to accomplish. I am simply trying
to remove the Receive-As permission for the admin user that I just created.
Once again, I am very new to Exchange and Powershell, but if there is any advice anyone has, it would greatly appreciated.

Answer 1

I ran this command, and a very long list was displayed, it looks like everything is there.
The weird thing is that I was able to run a previous command which granted Receive-As access to the user I am creating: 
Get-ExchangeServer | Add-ADPermission -User $newusername -accessrights GenericRead, GenericWrite -extendedrights Send-As, Receive-As, ms-Exch-Store-Admin -Confirm:$False 
The description for the commands to run read to 'grant permissions and to revoke denies, if present'. I'm not sure what this means, but the second part of this pertains to the second command that I am having trouble with:
Get-ExchangeServer | Remove-ADPermission -User $newusername -Deny -ExtendedRights Receive-As -Confirm:$False