I haven't used any features which require Snapping so this is not a difinitive answer but I hope it might lead you to some kind of solution:
Settings > Options... > Digitizing
Check that the Default snap mode is not off. You may need to add a value for the tolerance.
Afterwards, you can access the options for snapping via Settings > Snapping Options...
This will give you a set of options from a new dock window which opens at the bottom of the main window shown in the following image (this is assuming the snapping options opened in a dock window box is checked from the Digitizing options shown in the first image)
Play around again with the values/options and hope that something works!