The hand wheel just stays put while the inside of the machine seems to be moving, like something is slipping.

Is there a clutch that allows you to move the fabric through without the needle stitching (usually a knob in the centre of the wheel. That could be loose or worn.

the "hand wheel" on a sewing machine is meant to only advance the mechanism far enough to thread and set the needle , the motor should be used to run the machine else wise , as its turning every thing inside the machine to keep all the functions in "TimE" as models increase in there complexity there hand wheels are harder to move as more stuff needs to be kept in "time" now , also on some models the bobbin winder is directly powered by the hand wheel , if its not in use it should be disengaged completely

check that the little wheel inside the hand wheel at the end of the machine is tight and has not been loosened to rewind a bobbin
if it is then check if the hand wheel moves and if not , then check for thread jamming the shaft behind the bobbin carrier
failing that have it serviced by a sewing machine mechanic

Test: Put needle on straight stitch. Put needle all the way to the left and turn the hand wheel forward.
Now move the needle to the right and do this again.
Did the hand wheel move all the way for one of the two sides the needle was placed?
If your answer is yes then you need to get the machine timed.
Also, make sure that your brake used for winding the bobbins is tight. If it is tight then loosen the small screw (usually on front of hand wheel). Move the brake forward a little more to tighten and then tighten the small screw again. Look at my picture.

it's possible that something has broken or come loose inside the machine and the machine needs to be checked..

If the needle doesn't move even when you turn the flywheel ( on the end of the machine), you may have a slipped or broken belt.
If you have a mechanical machine, take off the top and look. If it slipped, you can put it back on using a flat screw driver to put it on.
Otherwise, take it to a reputable shop to have it fixed.
Electronic machines MUST be taken to a shop to make sure the warranty stays in force, and if you take it apart, some repair shops won't touch it.

Something is binding up inside. Clean and check under the presser foot and bobbin area. Really examine under there... look for threads wrapped around and in between moving parts. Also check in the slot for the take up lever... sometimes threads get balled up inside there can cause problems.

could also be a bent upper arm inside the machine (lets hope not) Get professional help if cleaning doesn't free it up.

it's possible that something has come loose or broken on the inside of the machine.
the name & model number of the machine is not shown, if the machine is mechanical it probably has a handwheel clutch,, make sure the smaller inner knob is tight. then try to sew again
if you still can't sew then I suggest you have the machine checked, because it's not reponding like it should

In the middle of the stop motion screw wheel there is a screw, undo the screw and unscrew the stop motion wheel all the way off, you will now see a three pronged washer, take it off and put it in a different position, put the stop motion wheel back on and just tighten finger tight, tighten the small screw all the way, now loosen the stop motion wheel and press on the foot control gently, the balance wheel should move with moving the machine, if the machine turns then start over again, you can put the three pronged washer upside down if you wish.

well,it seem that your upper camshaft was stuck due to several factor on mechanical linkages and maybe on gears.You have to isolate the checking since you have clean lower bobbins free from dirt and thread/fabrics chips.If there an opening on top of machine open it to check some mechanical destorsion or breakage.Check some broken gears inside.If nothing try to open also at the bottom of machine cover and there are also belt and gears connected to the motors and bobbins shuttle holder if so oil all shafting oil port,oil port bushing specially on bushing near hand wheel there is port for oil,
check also motor assembly of machine,you can disconnect belt from motor release the bolt holding motor adjust to lower tension belt and release the belt.Take some tools such as monkey pliers or small pipe wrench that can hold hand wheel just crack in order to move suddenly after oiling for several hours sometime bushing and shafting rushes emerged or if you have anti rush spray put in on.After cracking and you can move a little crack only by your hand several time lleft and right until all linkages free from rush.If you can move all parts and hand wheel rotate freely.Check also motor by rotating the small pulley conncted to motor if free to move.if ok put back and reassembly all parts disconnected.try to move again by hand if free to move after all asssembly.Run machine using foot pedal.