I got a Janome QC6260 for Christmas and have only been using it for a few weeks, and not very much on top of that.
Yesterday I dropped the feed dogs with the lever on the front to test it and then left it because I didn't have a practice sandwich for trying stitch in the ditch or waves. Tonight I went on to test the walking foot nad see how I get on with quilting on it, and the feed dogs won't come back up. In fact, if you press the pedal it starts hammering the needle down really quickly and will continue for a bit even when you take your foot off. :-(

I dropped the feed dogs on my new Pfaff recently and they wouldn't come up. I ended up taking the cover plate off and found a regular mattress pad of lint under it that apparently got dislodged when I dropped the dogs. Once I took all the lint out, it cleared the channel and the feed dogs popped up without a problem. May be worth a try. (I didn't think I had sewed much either,)

Try hitting the lever again. With my bernina. I hit he button for the feed dogs again and then press a little on the foot pedal to re-engage the feed dogs. It sounds like your feed dogs haven't re-engaged. Check your manual. I'm sure it's not broken..probably just a user error!!

Thanks, I'll try cleaning it. I did check the manual and it says nothing about it, just how to drop them with the lever button.

oh no, hope it is something easily fixed. Is your dealer close by?

Well, I am having stupid day or something...
I cleaned it and pressed the foot pedal and voila, the feed dogs came up. You'd think I was done now being an idiot, but no.
I read somewhere that it is good to change the needle to a denim needle in order to go through all the layers and that it makes the stitch straighter, so I am trying to change the needle, but when I try to push it down to get the bobbin thread it hits a metal surface just under the metal plate, and I can't work out why?
Took the needle out again several times, checked that it was straight (was new from a package anyway) and tried again. Any ideas?
I have changed needles on sewing machines hundreds of times and have never had a problem. I miss my really simply, if not rubbish low end machine.

Well, in town so not too far away, but in an awkward spot where parking is really far away and expensive and you have to carry the fairly heavy machine through an underground tunnel and halfway through town before you get to the store.
I am sure I'm just being stupid though :-D

Have you tried sewing with a regular needle since the feed dogs feasco?

If not try putting a regular needle in and seeing if the same thing happens. If not it may very well be the needle!

For the needle problem, I'd guess that either you have the wrong brand/type of needle for your machine or it is not inserted correctly (all the way to the top). Try changing back to the original needle. If that one works, I'm thinking you need a different brand of denim needle.

You do have the flat side of the needle facing back, don't you? And you have loosened the screw enough that you can be sure the needle is inserted up as far as it will go?

I just bought a sewing machine at the thrift shop -- great condition, clean, needle went up and down when I tried it in the shop, etc. I think the reason it was given to the thrift shop was because someone had inserted the needle wrong. As soon as I reinserted the needle correctly, it worked fine.

Make sure you are using the right size needle, not all sewing machine needles are the same length. Also you might not be getting it up all the way when putting it in its little slot. I worked for a Janome dealership for years and your problems are common and usually solvable. If you stick with Schmetz needles you will be safe! Clean and oil your machines regularly. Even oil them when your dealer says it is a self oiling machine, especially the cotton wick in the bobbin case if the wick dries out your machine will not work well. It only takes a drop or two of sewing machine oil.