After upgrade to 7.3, the "Subscriptions by Plan" report returns a wrong number of plan categories and their subscriptions.
Only subscriptions having promotions are shown in the report results. This behaviour was reported to the development team as an internal software issue PBA-85336.
No workaround is possible for PBA-85335. Contact the responsible Technical Account Manager or Pooled Technical Associate Team at firstname.lastname@example.org to clarify the status of PBA-85335 and request a hotfix.