senaite.health add-on is not supported since a long time ago, is not compatible with SENAITE LIMS 2.x. Install senaite.patient + senaite.diagnosis products for similar functionality.
Patient objects can be created via JSONAPI the same way as other content types. See CRUD — senaite.jsonapi 1.2.5 documentation
Related/duplicated: https://community.senaite.org/t/senaite-json-api-create-patient-with-api