2020 LG Gram 17 - memory upgrade won't boot
I have also tried booting the computer with just the onboard 8GB memory (the sodimm slot being empty) and the same behavior happens: no display signal. Putting back the original 8GB stick allows the computer to bootup into Windows.
I looked at the support page and don't see an updated BIOS which I was hoping would allow for memory upgrades, but there is none available at the moment: https://www.lg.com/us/support/product/lg-17Z90N-R.AAS9U1
Interestingly, the BIOS shows a wonky version for this computer: 17Z90N-R.AAS8U1, which is different than the version shown in the URL above. Attached is a screenshot that shows this.
I'm really hoping that a BIOS update is available soon that addresses this. My main reason for purchasing this laptop was to upgrade it to 24GB memory or possibly 40GB which the 2019 model supported. If I can't do this, I'll have to look elsewhere for a laptop