The stock item was unable to be saved. Please try again in Magento 2.x. This issue happend on new product add from admin panel. It is showing the Error is :
The stock item was unable to be saved. Please try again.

Solutions 1 :

Check your elasticsearch service status :

sudo service elasticsearch status    // for checking the Running Status
sudo service elasticsearch start    // for Start
sudo service elasticsearch restart    // for Restart

Solution 2 :

Please change all indexer as Update by Schedule mode in Admin Panel.

system-> index management