EA don't trade on Strategy Tester

 
Hello all

I wrote an EA that works ok with real time quotes (InterbankFX) but when I try to test it with Strategy Tester (ST), all attempts to buy or sell result on error 131. What can be wrong ?
 
see https://docs.mql4.com/trading/errors

131 is invalid trade volume
 
Hi stringo

I know the meaning of the error. The problem is this error does not appear with real time quotes but only when I test the SAME EA on Startegy tester...
 
Try to check "recalculate" button on the tester settings tab
 
I finally discover a way to make this work, but is rather strange. I need to connect online first, get some ticks and then try the strategy tester (ST) without closing MetaTrader.
And this symptom makes me wonder how to tell where the ST get its data to feed the expert under test ??
Reason: