I would take the bobbin case out and re-insert into the machine. You can try the hand-wheel while the case is out. Does it move?
There may be some helpful tips here.
https://www.juki.co.jp/household_en/...e%20manual.pdf
Next question for you. Not sure if this applies to your machine. I have brother/BL machines.
Was there a small round magnet under the bobbin case area? Make sure it went back in place.