An inactivity rule closes or deactivates an account after a set number of days without a trade. The clock starts on your last trade, not on your last login, so opening the platform does not reset it. Only a placed trade does.
The limit varies, and the consequence varies more. Some firms warn you first or reset the account. Others deactivate it outright with no restoration, which means the challenge fee and any progress are gone. AquaFunded, for example, deactivates accounts after 30 days of inactivity with no restoration.
This rule matters for traders who pause: after a holiday, a bad run, or a break to rethink a strategy. A month away can cost the whole account, including a funded account with profit still in it, if the firm's rule covers the funded stage too.
The common trap is assuming a funded account is safe while you take time off. Check whether the inactivity rule covers funded accounts as well as challenges, and place a small trade before any long break if the rule requires activity. Prop trading can cost you every fee you pay.