It's been a long time but, since I think I have made every mistake possible, I will try to remember some:

1) Mast raked way too far aft or forward, try putting the jib up first.

2) You are putting the pin in the wrong hole. Most links have a H14 and a H16 hole

3) Wrong link. I tried to use a H14 only link once, it didn't work. Plus other cats from the 70's used similiar things

4) Altered mast base or wrong mast base. Compare both sides of your mast base against a H16 known to be right. (an extreme case- we rescued an H16 with a ~28 foot mast off god-only-knows-what. The mast base was apparently put on with bondo)

5)(Most likely) Bent or crushed link

Hope it helps