It's been a long time since I've worked with Exchange, but it looks like the "Recoverable Items" folder is in the Non-IPM sub-tree of the mailbox. That folder contains sub-folders, too: https://learn.microsoft.com/en-us/exchange/policy-and-compliance/recoverable-items-folder/recoverable-items-folder?view=exchserver-2019
To reach those folders you'd have to add the folder name to the -Identity value:
Get-MailboxFolderPermission -Identity " testid@223.microsoft.com\RecoverableItems\Deletions"
Also, there's no space in the folder name. :-)