Recover deleted mailbox in O365

Simon,
What Shreedhar said is correct.  If the mailbox is not on litigation hold, after 30 days it will automatically delete.  I would  like you to also connect to o365 via powershell and run the following command to see if anything comes up.

Get-Recipient "DisplayNameoremailaddressoftheuserinquestion" -IncludeSoftDeletedRecipients | Select Identity,*Guid*

The powershell command doesn't work. Do I need to install anything ?

I can see the deleted AD account.... but how to restore the original mailbox ?

Thx.

post the error you get when running the command?
In O365 do you see the account in deleted users?

PS C:\WINDOWS\system32> $usercredential = Get-Credential
$session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential $usercredential -Authentication Basic -AllowRedirection
Import-PSSession $session -allowclobber
cmdlet Get-Credential at command pipeline position 1
Supply values for the following parameters:
WARNING: The names of some imported commands from the module 'tmp_4e5l4cdd.djo' include unapproved verbs that might make them l
ess discoverable. To find the commands with unapproved verbs, run the Import-Module command again with the Verbose parameter. F
or a list of approved verbs, type Get-Verb.

ModuleType Version    Name                                ExportedCommands                                                    
---------- -------    ----                                ----------------                                                    
Script     1.0        tmp_4e5l4cdd.djo                    {Add-AvailabilityAddressSpace, Add-DistributionGroupMember, Add-M...



PS C:\WINDOWS\system32> Get-Recipient "DisplayNameoremailaddressoftheuserinquestion" -IncludeSoftDeletedRecipients | Select Identity,*Guid*
The operation couldn't be performed because object 'DisplayNameoremailaddressoftheuserinquestion' couldn't be found on
'TY1PR01AxxxxxxAPCxxxxx.PROD.OUTLOOK.COM'.
    + CategoryInfo          : NotSpecified: (:) [Get-Recipient], ManagementObjectNotFoundException
    + FullyQualifiedErrorId : [Server=SG2PR01MB3271,RequestId=d7731267-39a3-44a1-87b0-2bec4f3fc431,TimeStamp=3/14/2019 2:05:2
   6 AM] [FailureCategory=Cmdlet-ManagementObjectNotFoundException] 168B39B,Microsoft.Exchange.Management.RecipientTasks.Get  
  Recipient
    + PSComputerName        : outlook.office365.com

Simon,
After Get-Recipient you are to put the user's email address or displayname. Read the command. Use the email address the user had.