Change accordion mode: Multiple vs Single active toggle
Divi Accordions Plus module can have two different modes: Multiple Active Toggles and Single Active Toggle.
The Multiple Active Toggles mode allows having multiple open/active toggles whereas the Single Active Toggle mode allows only one open/active toggle at a time (whenever a new accordion item is opened the previously open item closes).
The Multiple Active Toggles is the default mode.
To set the mode go to parent module settings Content tab -> Mode toggle and select one of the options provided by the Accodion Mode setting.