With Sora shifters, on your right shifter, the brake lever moves you to a larger rear sprocket. The thumb lever moves you to a smaller rear sprocket.
On the left shifter, the brake lever moves you to a larger front sprocket and the thumb lever moves you to a smaller front sprocket.
You're either at the extremes and can't shift anymore or you're not pedaling, in which case it won't do anything when you try to shift.
Catching his breath alongside a road near Seattle, WA USA
1999 K2 OzM, 2001 Aegis Aro Svelte
There was another recent thread on this subject. I also noticed your post about your attempts to inflate your presta valve tyres. Did you happen to get the bike from a bikeshop? If so then you might want to go back to them to have them show you how to operate some of your components.