Hey all, I'm pretty new to PC building but know the basics. I have an Nvidia GTX 1080 GPU and an older, Mini-ITX ASUS z791 motherboard. I know all PCI-e slots are one size, but I just don't feel like mine is in all the way (No, I do not have an SSD yet so I cannot check with task manager). The little plastic lock seems to be missing, so is that an issue? I was planning on getting a vertical GPU stand from NZXT (I'm using their H5 case). Does anyone know what my problem is or what I can do to fix it? Is there a way to tell it's in? Thanks!

https://imgur.com/gallery/gpu-wont-slide-into-pci-e-slot-4N1rIKh