If it is MT5 so delete all data (for EURUSD for example) from history folder (for EURUSD for example), after that - connect your Metatrader 5 to the account (it may be any demo account) and open EURUSD chart for every timeframe.
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If it is MT4 so there are 2 ways about how to load right data -
read this post -
How to prepare MT4 for backtesting/trading with some pair
https://www.mql5.com/en/forum/9950/page94#comment_4070616

- 2017.02.08
- www.mql5.com
when I try to run a backtest I get this msg 2019.01.19 20:22:26.233 TestGenerator: file "C:\Users\User\AppData\Roaming\MetaQuotes\Terminal\DA3C92B1779898CC0CACD726A655BECB\tester\history\EURUSD1440_0.fxt" cannot open [5]
a few days ago I downloaded some data and now I cant backtest anymore it seems like it cannot use the metatrader data anymore well I don't know hope someone can help me.
thank you.