Before you send your machine in for repairs try removing the keys that
are not working. Often some dirt or foreign particle lands under the
key and prevents its functioning properly.

To remove the key hold it by the edges and pull up, not forcefully, but
with enough energy to pop it loose. Thoroughly but gently clean any
accumulated debris on the keyboard bed (use an air blower or a soft
brush) and replace the key by gently pressing down until it engages.

Hope it works.