Make sure the needle is seated correctly and in the right direction. IIRC (it's been a while since I messed with mine) the needle is threaded from front to back. The long groove in the needle should face the front. I have a 600 series T&S. There are at least a few differences between mine and yours. My understanding is the 700 series uses the white tophat cams along with the black cams and can stitch patterns that require forward and reverse feeding of the fabric. Mine uses only the black cams and uses 2 pc plastic bobbins with the white markings. I'm not sure if your bobbins are the same. I learned the hard way that the bobbins need to be screwed together tight. Any gap can mess with how the thread feeds.
If all that seems fine, it's possible you have a timing issue but check the easy stuff first.
Rodney