Scheduling task on windows server 2016 using group managed service account failing

I have created a new group managed service account in AD and added two servers to access the account. I am able to use the account in services.msc. It is accepting it there but when I am trying to schedule task in Task scheduler (using PowerShell command) I am getting error that user name or password is incorrect.

Register-ScheduledTask : The user name or password is incorrect.
At line:4 char:1
+ Register-ScheduledTask myAdminTask –Action $action –Trigger $trigger  ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : AuthenticationError: (PS_ScheduledTask:Root/Microsoft/...S_ScheduledTask) [Register-ScheduledTask], CimException
    + FullyQualifiedErrorId : HRESULT 0x8007052e,Register-ScheduledTask

The command I am using is this:

$action = New-ScheduledTaskAction  "C:\Users\admin\Desktop\backup.cmd"
$trigger = New-ScheduledTaskTrigger -At 23:00 -Daily
$principal = New-ScheduledTaskPrincipal -UserID abc\gmsa$ -LogonType Password 
Register-ScheduledTask myAdminTask –Action $action –Trigger $trigger –Principal $principal

I am using the right syntax for username (domainname\serviceaccount$).

FYI : I am testing this on win server 2016 on azure cloud.

Found the solution for the problem. Only thing that needs to be done after added the computer in a security group which access group managed service account is to reboot the server once to reflect membership changes. After reboot I was able to add the account using powershell.

P.S :- Thanks for your reply postanote, I really appreciate it. :)