testing trading system

 
Hello,
I test Experts who come from the Market ...
some work well on MetaTrader Demo Account. and have good result.
when you test them on the other accounts it returns error messages.
is there an explanation? can we trust?
 
Ask the seller about it (because the discussion about the Market products is prohibited on the forum sorry).
A store of MetaTrader 5 trading robots
A store of MetaTrader 5 trading robots
  • www.mql5.com
An official showcase of applications for trading from the terminal
Reason: