Open it up - you may find that the 110v lead wires are burned as I posted about a year ago. Unplug the fireplace, remove the top (there are many, many screws) and follow the 110v wires into the unit. Here, you will find a connector block and this is where the hot side wire may be burned and not making contact, anymore.
Also, since Dimplex has a 2 year warranty and they are responsive, call them. Their contact information is:
http://www1.dimplex.com/contact.aspx