One of the products I received is hard or clumping together, is it still okay to use?

Yes, pure powder tends to clump, harden, or stick together. Other than making it a little more difficult to work with, there is no harm, nor does it mean the product has gone bad.

In addition some products may also smell, look, or taste different than you're used to depending on things like differents suppliers or even the raw material (roots or flowers) a product may be extracted from.