Cannot scroll right or left when "all apps" selected.

I cannot scroll to the right or come back to the left when I select "all apps". This is a change as somehow this selection was changed by me inadvertently. When I open "all apps" I can only scroll down and the matching letter appears on the right side i.e. A thru Z as I move my finger. Previously I swiped my finger to the left and a new app screen appeared. To go back I would scroll to the right. Now, I can only scroll down to see all apps. Changed something somehow and don't know how to get back.

Thanks in advance for the assistance. BC