It sounds like you’ve done all the right things to check for RAM. Unfortunately, the Notebook 7 Spin NP730QAA usually has its RAM soldered to the motherboard, so there aren’t any removable sticks to upgrade. If you have 8GB, that’s likely the max for this model.
If you're looking to boost performance, think about upgrading to a [link|https://www.predatorstorage.com/products/predator-gm7000-pcie-4-ssd.html|DDR4 SSD] if you haven’t already. It can make a noticeable difference! Good luck!