With the bobbin case out of the machine, touch the cutter button. Do you see the cutter arm move from left to right and then back left. If not the cutter arm is out of place. If it does it is something else.
I usually check two things:
1 - your cutter blade might be missing or dull and needs to be replaced. I would not recommend doing this yourself unless you are very good.
2 - many times there is lint or loose threads around the cutter in the area to the left of the needle plate that needs to be cleaned out. You can remove the cover to this area by first removing the needle plate and bobbin case. Then the cover is accessible to pop off by sliding the tip of a small screw driver under the cover at the bottom right corner of the cover. There should be a little opening. Carefully pop the cover off but be careful that the blade mechanism does not come off too. With your finger carefully hold the silver metal blade area steady and pick out the loose threads/lint from around the copper looking metal part. There is velcrow on the tip of the copper metal part so be sure that you don't remove that too. That's what holds the thread for the blade to cut it. If velcrow is missing, or the silver metal part is out of place that could be the problem also.
I recommend that any repairs/service be done by an authorized Viking dealer. You can find a local dealer by checking the Viking website at http://www.husqvarnaviking.com/us
and going to the Locate a Dealer link.