You didn't mention the type, style, fiber, and backing of carpet and thickness but generally the nap lays in one direction from the mill and a good installer will make the seams so they lay in the same direction so the seam isn't so noticeable. The seam will be like the parting of the red sea when the nap goes in opposite directions. If he didn't do it right, then have them back to fix it.
A good short nap commercial carpet can be expensive. Most use a limited color and pattern arrangement so you don't notice the seams. The description in your second post almost sounds like the carpet tape being glued to a cheap backed carpet and the glue bled through. They hopefully should have some type of satisfaction guarantee.
Otherwise the board isn't set up to cc to email and is designed as a public education to help all people who have similar questions but just haven't asked.