Tax reform eliminated the deduction for union dues for tax years 2018-2025.
Per the IRS Instructions for Schedule A:
No miscellaneous itemized deductions are allowed. That means you can no longer claim miscellaneous itemized deductions, including the deduction for unreimbursed job expenses, such as union dues. Miscellaneous itemized deductions are those items that would have been subject to the 2% of adjusted gross income limitation.