Not filling the order - HELP

 
This is the code:
trade.Sell(fixed_lot,act_symbol,info.Bid(),0,0,"Sell")


I don't have any problem usually, but sometimes, in the strategy tester this error appear.

2022.10.08 17:39:52.144 2022.09.05 01:36:00   requote 0.99053 / 0.99055 / 0.99053 (instant sell 0.1 EURUSD.Renko.ATR8.0 at 0.99052)
2022.10.08 17:39:52.144 2022.09.05 01:36:00   requote 0.99053 / 0.99055 (instant sell 0.1 EURUSD.Renko.ATR8.0 at 0.99052)
2022.10.08 17:39:52.144 2022.09.05 01:36:00   CTrade::OrderSend: instant sell 0.10 EURUSD.Renko.ATR8.0 at 0.99052 [requote (0.99053/0.99055)]

2022.10.08 17:39:52.144 2022.09.05 01:36:00   Alert: Sell Order Error Code: 4756


Why from time to time I get this error?

Moreover CTrade Class only send Instant Execution type Orders, how can I change it to use Market Execution?

 

Re-quotes are common in "Instant Execution". It is normal. Is due to slippage and the maximum allowed deviation for orders. Please do a search on the forum. There are many, many threads on the question.

You can't change from "Instant Execution" to "Market Execution". That is defined by the broker. Either change account types or change broker.