The code is this from you`r post , [EUR/USD::S] it`s a short , the size is not the problem , i tried again today the same thing.
Could be a broker restriction? i use solidary markets

I tried with GoMarkets, the same problem


Trade: KKT EUR/USD 10.11.2016
Error 062: Can't open KKT_EURUSD.par (rt:2)
Lookback period (100 bars) .

[317: Thu 10.11.16 14:56] (1.08695).
(EUR/USD::L) 14:56 Can't open 5@1.0872

[318: Thu 10.11.16 14:57] (1.08716)
[319: Thu 10.11.16 14:58] (1.08748)
Session stopped at 14:58
Logout.. ok


mt4 message :####'2000094040': order sell market 25.00 EURUSD.bo sl: 0.00000 tp: 0.00000

#################'2000094040': order sell 25.00 EURUSD.bo opening at market sl: 0.00000 tp: 0.00000 failed [Trade is disabled]