Tile under Shower Door

Hello,

I recently purchased a house, and in the master bath there is a glass shower door (quite heavy, ~30-40 lbs, which is placed on a raised ledge. The floor on the bathroom is ceramic tile. For some reason, the tile on the ledge where the shower door is installed was removed, so I removed the door, removed all the tile on the ledge, and then reinstalled the tile using tile adhesive, and grouted the grout lines and reinstalled the door.

Everything was fine, until this morning, when I saw where the tile where the shower door was resting was cracked, causing the grout to crack.

My question is, should I have used a different tile mortar that can support the weight of the door? If so, can anyone advise me on which kind of mortar to purchase? Any comments would be helpful. Thanks in advance.

You should use thinset to set the tiles and wait 24 hours before grouting and installing the door. Since the tiles were removed, could you tell how the curb was built?

Shower doors don't "rest" on the tile dam/curb. Tile adhesives don't cause tiles to crack.

What type of adhesive did you use? - Let's start there.
How is the door really supported? What type tile are you using? Are you stepping on the curb to enter and leave the shower?

Mortar is always better in wet areas than mastic this is where I see your mistake happened