Import error "Invalid parent WBS IDs"

Importing version 18.8 into both 20.12 & 21.12

Receive error in the Import Log

Import Failed: The import file contains projects with invalid parent WBS IDs. The following WBS nodes do not have valid parent_wbs_id in the WBS_id field

When looking at notepad, the parent_wbs_id is listed as "0.0000 0.0000"

None of the other WBS have that same value listed.

Any suggestions on how to get this to work or what to ask client to do differently during their export? Thank you