Magento 2.1 Errors

Our website is Magento 2.1: [login to view URL] Our home page has recently broken and we don't know why. We are getting this error and need somebody to fix it. Fatal error: Uncaught TypeError: Argument 1 passed to Magento\Catalog\Model\ResourceModel\Product\Collection::getEntityPkName() must be an instance of Magento\Eav\Model\Entity\AbstractEntity, instance of Magento\Catalog\Model\ResourceModel\Product\Flat given, called in /home/spacecollective/public_html/vendor/magento/module-eav/Model/Entity/Collection/[login to view URL] on line 1377 and defined in /home/spacecollective/public_html/vendor/magento/module-catalog/Model/ResourceModel/Product/[login to view URL] Stack trace: #0 /home/spacecollective/public_html/vendor/magento/module-eav/Model/Entity/Collection/[login to view URL](1377): Magento\Catalog\Model\ResourceModel\Product\Collection->getEntityPkName(Object(Magento\Catalog\Model\ResourceModel\Product\Flat)) #1 /home/spacecollective/public_html/vendor/magento/module-eav/Model/Entity/Collection/[login to view URL](1485): Magento\Eav\Model\Entity\Collection\AbstractCollection->_addAttributeJoin('featured', 'inner') #2 /home/spacecollective/public_html/vendor/mage in /home/spacecollective/public_html/vendor/magento/module-catalog/Model/ResourceModel/Product/[login to view URL] on line 1587