How can I open my sliding patio door from the inside?

The latch we lift up to open the sliding patio door from the inside will not lift up. I went outside and tried both keys but that did not help. Seem like the latch we need to lift up is stuck or the mechanism, latch, that it lifts is stuck. The door is new, about 3 weeks since installation. When you close the latch at the handle, two "hooks" come down to secure it shut.
Does anyone have any ideas what the problem might be?