Solución problema prestashop

Estuve configurando mi tienda prestashop ( https://tienda.saamiseg.com/ )y se me presentó un problema que requiero apoyo para solucionar:

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(1/1) ContextErrorException
Notice: Trying to access array offset on value of type null

in Module.php line 300
at ModuleCore->__construct()
in mercadopago.php line 77
at Mercadopago->__construct()
at ReflectionClass->newInstance()
in Container.php line 123
at Container->makeInstanceFromClassName('mercadopago', array('mercadopago' => true))
in Container.php line 153
at Container->doMake('mercadopago', array('mercadopago' => true))
in Container.php line 166
at Container->make('mercadopago')
in ServiceLocator.php line 65
at ServiceLocator::get('mercadopago')
in Module.php line 1191
at ModuleCore::coreLoadModule('mercadopago')
in Module.php line 1170
at ModuleCore::getInstanceByName('mercadopago')
in Hook.php line 911
at HookCore::exec('displayHeader')
in FrontController.php line 598
at FrontControllerCore->initContent()
in IndexController.php line 37
at IndexControllerCore->initContent()
in Controller.php line 306
at ControllerCore->run()
in Dispatcher.php line 518
at DispatcherCore->dispatch()
in index.php line 28