Quick update for future reference --> It seems that Polar only starts syncing the nightly HRV actively once it establishes a baseline for your nightly recharge.
Once the nightly recharge baseline was established 2 days ago the HRV synced flawlessly. Seems that I was just a bit too impatient.
Resting Heart Rate is still not syncing over, unfortunately. Just the nightly average HR & respiratory rate via sleep information.