Installed Ubuntu but no Grub

I have installed Ubuntu 16.04 from a USB onto my Acer Aspire R5-471, but I am unable to access the Grub menu. I have even run Boot-Repair from a disk but it am still unable to access the grub menu. Additionally, I have disabled fast-booting (some new feature on windows) and secure-boot. I have also tried the command

sudo grub-install --boot-directory=/mnt/boot /dev/sda

grub-install: waing: this GPT partition label contains no BIOS Boot Partition
grub-install: waing: Embedding is not possible. GRUB can only installed in this setup using blocklists. However, blocklists are UNRELIABLE and their use is discouraged.
grub-install: error: will not proceed with blocklists

Any suggestions? I think it might have something to do with my system's GPT or UEFI