Upper thread will not pick up the thread from the bobbin

Hook timing on a machine is very specialized and is a skilled job. Take it in and ask to collect next day and explain why.

Is the thread breaking? Most sewing machine issues are caused by incorrect threading or incorrect bobbin tension and upper thread tension. Another reason could be that the bobbin carrier and shuttle are not properly latched in.

Or the machine just needs servicing and the timing done.

Are you saying that the upper thread is not pulling the bobbin thread up to the top?

Install a brand new needle.

Remove the thread. RAISE the presser foot and rethread from the beginning--allows the thread to seat completely in the upper tension disk.

Check that the bobbin thread is inserted in the bobbin case facing the correct direction and that the bobbin case is threaded correctly through the bobbin case tension. Be sure to leave at least a 6" tail of thread on both the upper and lower threads.

Retest.

If it is still not picking up the bobbin thread, the bobbin case may be defective/malfunctioning or your machine probably needs professional service.

Remove the upper thread from your machine.

RAISE the presser foot and then rethread from the beginning. Raising the presser foot releases the tension disk so the thread will seat properly). Also, verify that the threading steps are correct (consult the threading instructions).

Check that the bobbin thread has been loaded in the bobbin case properly and threaded through the tension spring.

Test. If the upper thread is still showing under the fabric, tighten the upper tension disk until the upper and bobbin threads meet in the middle of the fabric.

...

probably sewing through the heavy jeans pushed the needle up to far. Loosen the screw that holds the needle and lower it down a little

have you lubricated your machine and bobbin case area? have you checked thread tension on both upper and bobbin thread? Too tight at the top can cause the thread to break. Poorly lubricated or improperly seated bobbin case can also break threads. Also if your needle can be moved left or right, and it's set off-center that can break threads. Good luck.

try a new needle
make sure the bobbin is not warped
make sure the bobbin case area is free of lint or loose thread
make sure you hold the upper thread tail while it's going down to pick up the bobbin thread
make sure there is a 2 to 4 in tail for the upper thread to grab

Re-thread, re-install the bobbin, change to a new needle.

If the problem continues the machine may need to go into the shop for service.

my wife's hd110 singer machine is not keeping tension. what can I do/ look at to try and help this

I cleaned the machine good with canned air, oiled it. I took out the bobbin case and cleaned it good also. I then noticed the tension screw on the bobbin case was loose, tightened it and the problem was fixed.