Hi @giggles6701,
Welcome to the Bunnings Workshop community, it is fantastic to have you with us.
As grout is an inflexible material, and corner junctions experience slight movement, grout will crack if it is used in a corner.
To fix this issue, I would suggest removing all of the grout used in this corner using a Grout Saw, and replacing it with Wet Area Silicone Sealant, which is flexible and is what should be used at tile corner junctions.
If there is grout used along the seam where the floor meets the wall, this should also be removed and replaced with silicone.
Check out How To Silicone a Gap for some guidance on the process.
If you have any further questions, please don't hesitate to ask.
Jacob
