Cross tenant move is not supported when the source user is in Litigation Hold, In-Place Hold or Rest

Dear mickeymitic 

Check for mailbox current status 

Get-Mailbox -Identity "identity" | Format-List DisplayName,Name,IsInactiveMailbox,LitigationHoldEnabled,LitigationHoldDuration,InPlaceHolds,RetentionHoldEnabled,RetentionPolicy

There are three Possibilities at source mailbox,

1-mailbox has legal hold 

Connect-exchangeonline 

set-mailbox -identity <identity> -litigationholdenabled $false

2-mailbox is part of Inplace hold 

Connect to exchange online powershell 

get-organizationconfig | FL Inplaceholds

3-mailbox is part of retention hold via MRM policy 

get-mailbox -Identity <identity> | select *policy*

set-mailbox -identity <identity> -RetentionPolicy $null

The only place you will have to put effort would be find the guid of the inplace hold and then disable it,

Also please ensure that your mailbox properties are like below,

PS C:\Windows\system32> get-mailbox -Identity rahil | select *hold*

LitigationHoldEnabled : False
RetentionHoldEnabled : False
EndDateForRetentionHold :
StartDateForRetentionHold :
LitigationHoldDate :
LitigationHoldOwner :
ComplianceTagHoldApplied : False
DelayHoldApplied : False
DelayReleaseHoldApplied : False
LitigationHoldDuration : Unlimited
SCLDeleteThreshold :
SCLRejectThreshold :
SCLQuarantineThreshold :
SCLJunkThreshold :
InPlaceHolds : {}
RecipientThrottlingThreshold : Standard

If you found the response helpful, please mark as an answer,

Regards - Hasan Reza