Make sure the presser foot is up, then try pulling the thread thru. If it still is really tight, make sure that the thread is going between the tension disks, not in back (next to the machine) or in front (next to the tension knob) of them. Although it's hard to do, I once threaded mine with the thread going in back of the disks. If it's threaded correctly thru the disks, then tug on the thread just before going thru the tension disks. Sometimes it's caught up somewhere closer to the spool.
I rarely thread the machine any more. I cut the thread at the spool, tie the new thread on and then slowly pull it thru to the needle.
Knock on wood, I've had great success with my TL. It will sew with any thread and the tension is easy to adjust.