Although millions of tax returns are successfully e-filed every year, some returns simply can't be e-filed or keep getting rejected even though there's really nothing wrong with them.
For starters, you can't e-file returns that contain: overrides, have no taxable income, box 1 of the W-2 is blank, or box 16 exceeds box 1, IRS forms not on the IRS's Modernized E-file list, and many nonresident and part-year state returns.
(Not to mention tax returns that contain non-finalized forms, prior-year returns, amended returns, and the 6th return you try to e-file in the TurboTax software.)
Then there are those returns that keep getting bounced back because somebody already claimed a dependent or because of incorrect information at the IRS.
For these types of situations, there's really nothing you can do to "fix" your return so you can e-file it. For this year at least, you'll need to file a paper return instead.