How the lock works
When you buy a robot, you enter the account numbers it may run on. Our build computer puts them into the robot file in a scrambled form, together with the last four digits of each, and builds the file for you.
When the robot starts, it reads the account MetaTrader 5 is logged in to and compares it with its list. On one of your accounts it writes one line in the Experts tab naming them, and runs. On any other account it does nothing: no trades, no chart buttons, no messages. It shows a message on the chart, writes it once in the Experts tab and shows one alert, so a refused robot never looks like a running one.
If MetaTrader is not connected yet, the robot waits and looks again every few seconds. It checks again at every tick, so logging in to another account stops it at once.