Cannot delete database, tried all common solutions!

get-mailbox -Database db21 -archive
get-mailbox -Database db21 -Arbitration
get-mailbox -Database db21 -Archive

Get-MailboxStatistics -Database "db21" | where {$_.DisconnectReason -eq "SoftDeleted"}
Remove-mailboxdatabase -id db21
This mailbox database contains one or more mailboxes, mailbox plans, archive mailboxes, or arbitration mailboxes. To
t a list of all mailboxes in this database, run the command Get-Mailbox -Database <Database ID>. To get a list of all
ailbox plans in this database, run the command Get-MailboxPlan. To get a list of archive mailboxes in this database,
n the command Get-Mailbox -Database <Database ID> -Archive. To get a list of all arbitration mailboxes in this databa
, run the command Get-Mailbox -Database <Database ID> -Arbitration. To disable a non-arbitration mailbox so that you
n delete the mailbox database, run the command Disable-Mailbox <Mailbox ID>. To disable an archive mailbox so you can
elete the mailbox database, run the command Disable-Mailbox <Mailbox ID> -Archive. Arbitration mailboxes should be mo
d to another server; to do this, run the command New-MoveRequest <parameters>. If this is the last server in the orga
zation, run the command Disable-Mailbox <Mailbox ID> -Arbitration -DisableLastArbitrationMailboxAllowed to disable th
arbitration mailbox. Mailbox plans should be moved to another server; to do this, run the command Set-MailboxPlan <Ma
boxPlan ID> -Database <Database ID>.
    + CategoryInfo          : InvalidOperation: (db21:DatabaseIdParameter) [Remove-MailboxDatabase], AssociatedUserMa
   lboxExistException
    + FullyQualifiedErrorId : 691D542A,Microsoft.Exchange.Management.SystemConfigurationTasks.RemoveMailboxDatabase