‘Show Sampling Ring’ greyed out in Photoshop

Hi all!

I've been having a few minor issues with tools in photoshop lately and I can't pinpoint the cause of them. I use a MacBook. 

The one giving me the most grief is the Sampling Ring not showing up when I'm using the eye dropper tool, or when I'm holding down alt in the brush tool. 

After a lot of searching, I read somewhere I should check the 'Show Sampling Ring' option in the eyedropper tool was ticked, but when checking I can see it's not ticked and it's actually greyed out. 

I have no idea what the cause of this was but it only happened very recently and I can't seem to get it to work! 

Does anyone have any input at all? 

I'm not sure if this will help find the root of the problem, but another small issue that happened the exact time this issue did, is that the line that shows up when I use the curvature pen tool (which is typically a light-ish blue and very easy to see) has gone to a weird grey, almost see-through colour. 

thanks so much everyone! Appreciate any input at all.