All of my recent snipe did not go off.
ebay user: $sieuquay$
One example:
item# 150346088539
Winning bid: US $2.25
Snipe: $4.00

If you check "My Status" field of your snipe, you will see that your password was too weak.
Please check this link for more information on the guidelines how to make your password stronger:
http://www.myibay.com/forums/viewtopic/1316/short-or-weak-password-will-prevent-you-from-bidding/

I think I know what went wrong. My eBay password has been changed recently. I forgot to update it in myibay account but it's strange that myibay still let me login and schedule snipe as normal.

It has no way to find out that your changed your password so you have to keep it in-sync (just loging in with your current password will work).

Thank you for follow up and good luck sniping!