I’ve used Shift + G to loop a selection for many years but on Cubase 9 if I highlight a part and press Shift + G it collapses the track height instead of looping the selection. Does Shift + G still loop a selection in Cubase 9?
It has another hot key alt+p now, option name is Loop and Play, search in hot keys and rebind
Awesome thanks 
SHIFT-G still works for me (9.0.20).
I wonder if it got inadvertently reassigned to another function.
You could open the key command list, type in SHIFT-G, and see what Cubase has it assigned to.
Alt P is such a bad choice for a sort cut key, they couldn’t be further apart. I use a Macro on ‘/’ Loop Selection and Play… As the Num pad ‘/’ is cycle on off. I should be uploading my print out and KeyCommands file soon. Lots of Logical improvements.
The default for Shift-G is zoom out vertically, has been since I can remember. No reason you can’t change it to what you want it to be.