I have repaired a vertical crack over my slider three times now and the crack continues to reappear. The first repair I just put spackle on it. The second I used new tape but left the original tape there. The third time I removed the second tape and replaced it with mesh tape and the crack has returned again approximately four months after the repair.
What am I doing wrong and what do I have to do to eliminate this crack so I can paint?
You need to remove all the old tape, spackle, and joint compound to repair this joint. I would use fibreglass mesh tape and then apply the joint compound over that. You will to apply at least 3 coats of compound to feather it out far enough so as not to see the joint and lightly sand the last coat to smooth out any rough edges. The prime the area with a latex drywall primer before putting on your finish coat.