Paste the full cmdlet and the full error message please. If I have to guess, you're providing an incorrect/incomplete folder id. Keep in mind that folder names can be localized, so use the correct value there. If needed, use the
Get-MailboxFolderStatistics cmdlet to get the folder name(s) for a specific user.
For example, on a mailbox with German localization, this will not work:
Instead, I have to use this: