I can't see your tax return to tell you why you owe this year versus last year. However, there may be several reasons why you may have a shortfall. The following are some suggestions to help you find the reason why.

• Double check the amounts you entered into TurboTax to make sure they were entered correctly.
• Do an income tax return line by line comparison to see what is different this year versus last year.  
• Your 2020 federal Tax Withholding was lower than 2019.  
• You deferred less income into your Employer-Sponsored Retirement Plan or Flexible Savings Plan.
• You didn't qualify for a tax credit you received last year (or the credit amount decreased).
• You removed a dependent.
• You changed your filing status.
• If you itemize, your Itemized Deductions are lower this year. or the standard deduction is lower.

If you have two W-2's in 2020, see Why did my refund drop when I entered a second W-2?

I went through line by line and the only amount that changed were my 401 contributions. I can’t imagine why increasing those would cause my taxes owed to double. 

*for clarity. I paid the same amount of federal taxes this year as I did last year but now I owe $ where last year I was receiving a refund.

Increasing your 401K investment amount would not result in increased taxes owed.  Something else has changed to result in your taxable amount being higher on the same amount of income.

@lowreyr