You have below options :
Enter Invoice Number in RefPrecedingDocumentDetails if you have in the Updated Excel file which we are sharing then delete current Import and Import Updated File Again.
If you don't want to enter invoice number contact admin
and tell him to save and next from import error page Invoice will be generated.
If you don't want to contact admin and don't want to enter RefPrecedingDocumentDetails delete current imported file from actions. Disable below settings>>import and Import file again it will generate Invoice without warning of RefPrecedingDocumentDetails.