If snap to guides doesn't appear to be working, check the following:

•The snap to guides is actually turned on in the Layout menu: the options need to be ticked.

•The snapping tolerance is not set at a number lower than 20 in your preferences (Edit > Preferences > Grid > Snapping tolerance): See Adjust snap-to zone for instructions.

•There are master guides on the master- the absence on the master guides on the master may compromise snapping to guides.

•You're not holding pressed SHIFT+CTRL while dragging (as SHIFT+CTRL temporarily disable snap).