I made a nondeductible contribution of $5500 to IRA in 2018 & converted $5502 to Roth. But Form 8606, line 17 is filled with 0... shouldn't it be 5500?

Line 17 will not have a value if there are non-deductible contributions on line 1 or line 2.

The 8606 line 1 should have the 2018 non-deductible contributions but will only if them of entered in the IRA contribution section as non-deductible contributions.

Enter IRA contributions here:
Federal Taxes,
Deductions & Credits,
I’ll choose what I work on (if that screen comes up),
Retirement & Investments,
Traditional & Roth IRA contribution.

OR  Use the "Tools" menu  (if online version under My Account) and then "Search Topics" for "ira contributions" which will take you to the same place.

Thank you - that was helpful! This article was also helpful: <a rel="nofollow" target="_blank" href="https://ttlc.intuit.com/questions/3582070-backdoor-roth-ira-contribution">https://ttlc.intuit.com/questions/3582070-backdoor-roth-ira-contribution</a>