After you run the Export-csArchivingData PowerShell cmdlet, encrypted files that are uploaded to conferences are returned without being unencrypted in Microsoft Skype for Business Server 2019. This issue affects all file types.
To fix this issue, install the December 2021 cumulative update 6 for Skype for Business Server 2019, Core Components.
Then, start the Skype for Business Server Management Shell:
Select Start, and then All Programs.
Select Skype for Business 2019, and then select Skype for Business Server Management Shell.
Run the following cmdlet: Set-CsConferencingConfiguration -EncryptArchivedData $false”