Will you help me in justifying the IRS letter saying "Proposed Amount Due $2590"

No one at TurboTax sees your letter or knows what it says.  The IRS does not tell TT when they send you a letter.  What tax year is it for?  What is the letter number or CP number?  What does it say?

(what the letters from the IRS mean)

I GOT A LETTER FROM THE IRS   

https://ttlc.intuit.com/questions/3605673-i-got-a-letter-or-notice-from-the-irs

1) Start at this link to understand What your IRS letter is saying: https://www.irs.gov/individuals/understanding-your-irs-notice-or-letter

2) Next, please share Which type IRS letter you have, and Why IRS suggests you owe them.

3) Where is your evidence indicating IRS is wrong? If none, agree and pay ...