Error when trying to transfer Workspace Ownership


I'm a system admin and needing to transfer the ownership of a Workspace over to a Licensed User however when I go through the standard steps (Sharing And Collaboration --> Workspaces --> Transfer the ownership of a workspace) I get the error "This user cannot accept ownership at this time. Please retain your ownership or select a different user." I tried transferring it months ago and was getting this same error but forgot to retry.

Can anyone help me figure out what I'm doing wrong?

Much appreciated.