What time must trades be closed by?

All trades must be closed before 4:59 PM ET.

Ags must be closed earlier to see the rules on when ags close see Are there any markets that must be closed earlier than before 4:59 PM ET – Apex Trader Funding

Keep in mind, some markets close earlier than 5:00 PM. 

Also, remember some markets close early on holidays.  Here is the current holiday calendar for your reference: https://www.cmegroup.com/tools-information/holiday-calendar.html

You can begin placing trades again at 6:00 PM ET.