I try to execute a script and after the message SUCCESSFULLY LOADED it gets REMOVED.
Scripts are usually designed to do only one task and then exit when they are finished. For example a script to close all open orders would try to close all open orders and once it is done it would exit. (it consists of a start() function to do its work and when this function returns MT4 will remove the script)
Code that is meant to stay on the chart is usually implemented as an Expert Advisor (EA, usually used for auto trading) or an indicator (to calculate and plot lines and other things into the chart).
There is probably a problem in the code! Check both the Journal log as well as the Experts log for any error message or warning or any clue as to why.
Also, check your code and its logic to make sure it is working correctly.
add this code #property show_inputs