First a couple of obvious checks.
1. If you click Tool > Options > and then export advisors are any of the “disable expert…” options checked. If so then uncheck them.
2. Right click on the chart with the expert advisor and then select the common tab and ensure that the allow live trading is checked
It also could possibly be a compilation issue. Is the .ex5 or 4 file showing in the Experts folder. You could try opening up metaeditor and compiling it manually and seeing if any warning shows up.
It sounds like it is just not opening trades? Are you positive that the entry conditions have been triggered?