I was not eligible for 401k contribution in 2018 but the software says I was so it is making my contribution to my IRA non tax deductible.

[MichaelL1]

Look at the W-2 and see if the box marked Retirement Plan in box 13 was checked by mistake.

If it is checked and the w-2 is incorrect you need to contact the employer to a corrected W-2.