I need to fix my tax return. It was rejected due to being claimed as a dependent. It says "fix my return" all over the place but just leads me to signing w/o fixing.

"It was rejected due to being claimed as a dependent".

If you are OK with being a dependent, go back to the personal info section and answer yes to the questions "can you be claimed as a dependent" and "Were you claimed".

If you are not OK with that, then you can NOT e-file.  You will have to mail in a paper return.

If someone else claimed you, as a dependent,  inappropriately, and if they file first, your return will be rejected if e-filed. You would then need to file a return on paper, claiming yourself, if appropriate. The IRS will process your return and send you your refund, in the normal time. Shortly (up to a year) thereafter, you’ll receive a letter from the IRS, stating that your exemption was claimed on another return. It will tell you that if you made a mistake to file an amended return and if you didn't make a mistake to do nothing. The other party will get the same letter you did. If one of you doesn't file an amended return, unclaiming the exemption, the next letter, from the IRS, will require you to provide proof. Be sure to reply in a timely manner.

Winner gets the tax benefits; loser gets to pay the IRS back with penalties and interest.

The usual suspects are:

1. The parent the child lives with.
2. The other parent. 
3. The child claimed his own exemption.
4. Some other member of the household (e.g. grandparent)
5. Someone else the child lived with for part of the year