Hey Virginia, I'm up in Baltimore... cheers brother.
I've also got a currently non-sparking AVL. Others have helped me immensely in this, so I thought I'd try and shoot a little advice your way. I'm no expert, and I'm sure the experts will chime in soon. I am a novice as far as wiring goes, so I'll spell this out in my own personal layman's terms. Apologies if some of this is incorrect, or is offensively basic.
1. When you tested the spark plug while it was unplugged, did you hold the threads of the plug against a cylinder fin? It needs that in order to ground the circuit. Apologies if this is all well below your comprehension level... again, I am a novice.
2. Are your lights working and everything, just no spark?
3. There is a little fuse holder in-line with a brown wire which connects to your TCI box. Open that little black plastic case up and check and see if that fuse is blown. Also, check and see if those tiny little wires attached to the fuse holder are broken. My recent 'no spark' issue was mainly due to that brown wire breaking off right at the fuse holder.
4. The plug is powered by a Coil. The coil is a little black unit along the front frame of your bike up under the gas tank. Follow the thick spark plug lead up from the aluminum cap spark plug cap. That coil has a 2-wire waterproof connector attached to it. It's hard to undo, but once you do, the brown wire should always be reading somewhere around 12v DC when compared to ground (bike frame). The other wire (red/white I believe) comes straight from your TCI box... my understanding is the Coil stores up energy from the brown wire, then the TCI tells it when to fire off that energy (red/white) and it fires off that stored energy via the spark plug lead. Dunno if this is correct or not, but it makes sense to me. If you don't have 12v or so at the brown wire, that's probably your culprit.
5. Have you disabled your side kickstand safety switch? That is a common no-start issue. It's a little wire (2 prong plug) down along your side stand. Just unplug that bad boy and leave it hanging, or tape it up to get it outta the way.
6. Attached is the wiring schematic for yours (and my) bike. I've got an '09 AVL as well. Love this damn thing but the electricals are frustrating. I believe the brown wire starts at the right-hand control switch on the handlebars at the kill switch. It comes out of the control cluster into the headlight casque, then runs the length of the bike, and splits in a Y... one leg goes to the TCI box (through the abovementioned fuse), and the other goes directly to the coil. If you've got no power at the brown wire at the coil, you can test it at the plug within the headlight casque too... just poke your multimeter into the back side of the connector.
I feel like this is a very roundabout synopsis, but just trying to share some of my little knowledge on the subject since others have shared so well with me. Others will also chime in with ways to test if your Coil is ok via impedance or something, and other possible issues you may have. Fingers crossed it's something easy like a blown fuse. Normally it is.
Cheers,
Chuck