My price limit was reached but trade was wasn't executed

The reasons for this could be many. 

The first one is that most public price sources, including the websites of the major stock exchanges, display delayed prices, with some even delayed by up to 15 minutes. 

The indicative prices displayed on Moneybase may also be delayed for specific markets. This means that if when raising you order you based your limit on a delayed price, it may no longer be reachable anymore moreso on days of higher volatility. This is because trade executions on Moneybase are transacted on real-time prices.

Other reasons may be that some stocks may trade on multiple exchanges, or that there may be different shareclasses of the same company trading on the same exchange with similar names.