The Merge Agent failed after detecting that retention-based metadata cleanup has deleted metadata at the Publisher for changes not yet sent to the Subscriber. You must reinitialize the subscription (without upload).
The merge process failed because it detected that retention-based metadata cleanup at the Subscriber has deleted metadata for changes that have not been sent to the Publisher.
Error -2147199402 may also be caused by other problems with the metadata, such as configuring the publication for aggressive cleanup or subscriber syncing outside of the retention period.
Reinitialize the subscription by using @upload_first = 'FALSE'.
The last sync date can be found in the sysmergesubscriptions table.