Hi,
I've recently installed Zorin OS, coming from Windows, everything has been brilliant so far but my PC has a second drive. I have the option to mount on boot enabled but it seemingly doesn't.
Any idea why this might be and how to fix it? (I'm new to linux and prefer use GUI's as much as possible).
I'm a noob as well. You'll find people here super-helpful.
Have you unchecked (i.e. switched off) the "User session defaults" in Disks/Settings (cog icon under the drive)/and checked "Mount at system startup"?
For reasons I don't understand the default settings don't seem to work in the way that you expect.
No guarantees, just a suggestion... 
Welcome to the Forum!
Are Secure Boot and Fast Boot in BIOS disabled? How is the Drive formatted? In the Settings that @DavidA has mentioned, You should also see if Your are the Owner of the Drive. Please check that.
Hi,
Thanks for the quick reply, the drive is formatted as Ext4, and Secure Boot and Fast Boot are disabled, I did what @DavidA said about the default settings and that worked. Would it be safe for me to enable secure and fastboot without anything in my system braking?
Was it enabled before?
No it hasn't been since I installed Zorin
Then, I would let it disabled. It should break the System when You disable it but could lead to some Issues and You could have to tinker to get it work. So, when it was already disabled, I would suggest to let it disabled.