After you enter your W-2, Continue through the interview until you reach the question Is this W-2 from the U.S. Armed Forces? Be certain you have answered the questions correctly.
The Tax Cuts & Jobs Act of 2017 repealed the Moving Expense deduction except for active duty military personnel, so unless your W-2 is issued through DFAS, you will be unable to claim a moving expense deduction. You will also need to contact your employer and request a corrected W-2, as Code P is now only used for military moving expenses.
If you are active duty military, you should be able to complete the moving expense section. Just type moving expenses in the Search box in the upper right, then click Jump to moving expenses. Thank you for your service.