Did you take the Standard Deduction for 2018? It's not only the charitable contributions but all your itemized deductions were probably not more than the new Standard Deduction.
FAQ on 2018 changes
https://ttlc.intuit.com/community/tax-reform/help/how-will-tax-reform-affect-my-federal-tax-return/0...
Deductions that have been suspended for 2018
https://ttlc.intuit.com/community/tax-reform/help/which-federal-tax-deductions-have-been-suspended-b...
