If your Eco-Hardshell Case for MacBook Pro 16-inch keeps coming off, the cause is nearly always a clip that never snapped in, especially the long clip on the bottom case. The Eco-Hardshell Case for MacBook Pro (ST-MBP16CL, ST-MBP16DR) installs as a two-piece snap-on shell, with 6 clips on the top case and 5 clips on the bottom case that all need to seat before the case will hold.

How to get your Eco-Hardshell Case for MacBook Pro 16-inch to stay on

1. Confirm you have the right size. The 16-inch Eco-Hardshell Case for MacBook Pro fits the 16-inch MacBook Pro models with M1 Pro, M1 Max, M2 Pro, M2 Max, M3 Pro, M3 Max, M4 Pro, and M4 Max chips. The 14-inch models use the 14-inch version of the case.
2. Check your MacBook model before going further. Click the Apple menu, choose About This Mac, and look at the model name, size, and chip.
3. Clean your MacBook Pro before installing the case. Dust and grit along the edges keep the clips from closing fully.
4. Install the top case first and press until all 6 clips snap into place. If the top case is on correctly, the logo sits at the bottom right.
5. Install the bottom case and press until all 5 clips snap into place.
6. Pay special attention to the long clip on the bottom case. If that long clip does not snap into place, the case will fall off.
7. Check that the vents line up properly. Misaligned vents mean the bottom case is not fully seated.
8. If a corner still lifts, take the case off completely, clean both the MacBook Pro and the inside of the case, then reinstall the top and bottom pieces one at a time, pressing along every edge until each clip clicks.