Crack The Dat Torrent How Come A Crack Formed In My Grout?

How come a crack formed in my grout? - crack the dat torrent

Just recently my bathroom and down a new subfloor (plywood) and cement backer board put renovated. The ground seemed to level, then let me Mortati tile.

Formed after pressing and dry, a crack in a line of white cement wall to another wall (approximately 6 feet).

Can I regrout following line in the cracks or do something else to fill?