I have a Husqvarna Classica 100. The bobbin case will not click into place. The inner section seems to have gone inwards.

SOURCE: Bobbins for Husqvarna Classica 100

classica 100 requires special husqvarna bobbins available from husqvarna dealers.

scott

SOURCE: viking husqvarna classica 100, thread tension

I suspect you are correctly threading the machine but the timing of the needle and bobbin hook is off. When the threaded needle goes into the bobbin area, a pointed hook grabs the thread and loops it with the bobbin thread. Something is catching when the needle starts to come up that is not allowing the bobbin thread to be pulled back through the needle plate opening by the upper thread. With machine threaded and bobbin in place, have the bobbin area open if possible and watch the thread interaction when the needle goes down. To set the hook/needle timing, normally covers have to be removed. Suggest taking it to an authorized Husqvarna Viking dealer for service. You can find the nearest dealer by click on the "Dealer" link at http://www.husqvarnaviking.com
Good luck.

SOURCE: I have a Viking Classica 100 and the hook just

Yes, these parts should be replaced. Original parts are only available from an authorized Husqvarna Viking Dealer. The service/repair is very intense and should be performed by a certified Husqvarna Viking service technician through the Dealer. You can find the nearest dealer by click on the "Dealer" link at http://www.husqvarnaviking.com
Good luck.