Restoring a managed SQL instance in Azure using PowerShell
This command is somehow not clear for PowerShell and there is problem to determine which version of the method is accurate.

However it should work if you specify -FromPointInTimeBackup switch, I have checked  it and got credentials error which is fine as I am not logged in to proper account.

PS C:\WINDOWS\system32&gt; Restore-AzSqlInstanceDatabase `
&gt;&gt;     -Name "SomeDatabase" `
&gt;&gt;     -InstanceName "our-oltp-dev" `
&gt;&gt;     -ResourceGroupName "dev-managedsqlinstances" `
&gt;&gt;     -PointInTime "4/7/2020 12:00:00" `
&gt;&gt;     -TargetInstanceDatabaseName "SomeDatabase_FROM_DEV" `
&gt;&gt;     -TargetInstanceName "our-oltp-sandbox" `
&gt;&gt;     -TargetResourceGroupName "sandbox-managedsqlinstances" `
&gt;&gt;     -FromPointInTimeBackup
Restore-AzSqlInstanceDatabase : Your Azure credentials have not been set up or have expired, please run
Connect-AzAccount to set up your Azure credentials.
At line:1 char:1
+ Restore-AzSqlInstanceDatabase `
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : CloseError: (:) [Restore-AzSqlInstanceDatabase], ArgumentException
    + FullyQualifiedErrorId : Microsoft.Azure.Commands.Sql.ManagedDatabase.Cmdlet.RestoreAzureRmSqlManagedDatabase


Additionaly, be sure that you use the latest version of Az.Sql module.

Update-Module -Name Az.Sql -Force