Max2Play Home 2016 (en) › Forums › General Questions on Hardware and Max2Play Versions › PowerFail, Corrupt SD, SD Protect not in HiFi Berry 2.46? & Stretch Incommicado › Reply To: PowerFail, Corrupt SD, SD Protect not in HiFi Berry 2.46? & Stretch Incommicado
The SD card protection does not work with LMS. So if you have LMS installed, this is the reason why.
You can also use the HTTP command for shutdown (displayed when you click it manually in the URL bar) to schedule or implement a correct shutdown without using the web interface.
What is the exact error you get when you try to install the SD card protection?
Regarding URL bar access to max2play: the slash at the end „max2play/“ should indicate that it is not a search request. At least this is the case with most browsers.