I just bought a janome mini sewing machine. I
First, in order to get the bobbin thread up, you have to turn the wheel backward, not forward. If you try this, and it is not the problem, keep going.
Next you need to check the needle. There is a screw on the right side of the needle carriage right underneath the underside of the top...unscrew this and the needle should come right out. The flat side of the needle shank should go towards the back of the machine. If it isn't, switch it so that it is and try again.
If this doesn't solve your problem, what has happened is that the gears in the machine have gotten out of alignment. There is an easy fix:
Take off the plate that covers the bobbin chase...there are two screws one on each side. Remove these...you need a stub screwdriver, because regular ones will not fit under there.
Remove the bobbin carriage and the bobbin, making careful note of how they fit back in. Take a picture before disassembling it so you have a reference.
The part that carries the thread around the bobbin is still in the machine. Turn the wheel and you will see it rotate. What has happened is that the needle is not going down in the machine at the right point because someone kept sewing after it jammed and one gear kept going while the other one didn't and now it is out of alignment. These machines have plastic gears and the can slip past each other if you aren't careful not to stop immediately when they jam.
To fix it, you are going to have to do some trial and error. Grab the rotating part of the bobbin chase and hold it firmly. Rotate the wheel forward until you hear it click once. Then rotate the wheel backward again and see if it grabs the top thread. If it doesn't, repeat holding the bobbin chase and turning the wheel forward until it does.
Once you have the gears basically aligned, you will need to reassemble everything. Put the face plate back on and put at least one of the screws in all the way. The face plate holds the bobbin chase in correctly and if you don't fasten it it will not work correctly.
Now try sewing. If it starts to jam, stop immediately, cut the threads and look at the back. If it's a loopy mess, you are going to have to dissamble as before and again grasp the bobbin chase and turn the wheel forward one more click, then reassemble and try again. Eventually, you will find exactly the right alignment and the machine will sew perfectly.
I just had to make this fix on my own machine...I didn't want to take it in for repair because the bench fee alone would cost as much as the machine did!
There are some great video's on YouTube for help with threading the machine...look for StampTV and you should find them. Good luck!