In early 2022 versions of Medilink 2022 (until 17th May) there was a bug affecting new Medicare Online Web Services IMCs whereby Pathology and Diagnostic Imaging (LSPN) items had their Request/Referral data removed.
This has since been fixed.
If you are billing those items please ensure you have the latest update.
At the time of writing you may optionally revert back to the old Medicare Online Adaptor system via Links Menu -> Configure Online Claiming then untick MCOL Web Services, then re-start Medilink. (Note: the old MCOL Adaptor (PKI) system may not be around for much longer.)