If none of the other solutions are working, check your database table inventory_source_item. If all the products have a status of 0 then update them to 1 and see if that helps.
UPDATE inventory_source_item
SET status
= '1' WHERE inventory_source_item
.status
= 0;
UPDATE `inventory_source_item` SET `status` = '1' WHERE `inventory_source_item`.`status` = 0;