The stock item was unable to be saved. Please try again. Magento 2.4.0

Please change all indexer as Update by Schedule mode in system-> index management. It's working for me.

If you are using Elasticsearch instead of Mysql. then please check once that elasticsearch is working or not.

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

I have fixed it. There was an entry missing in cataloginventory_stock

try to run this query

INSERT INTO cataloginventory_stock (stock_id, website_id, stock_name) VALUES ('1', '1', 'default');

Go to Magento 2.4.2 installation location:

cd /var/www/html

Flush cache

sudo php bin/magento cache:flush

Chek Indexer Status

php bin/magento indexer:status

Reset Indexer

php bin/magento indexer:reset

Reindex Indexer

php bin/magento indexer:reindex

Chek Indexer Status

php bin/magento indexer:status

Chek indexer Info

php bin/magento indexer:info

Finally Flush Cache

php bin/magento cache:flush

Restart sudo reboot

Login to admin and check

I've Migrated the magento 2.3.x into 2.4.x. I faced the same issues. I've resolved this issue the following way.

1. INSERT INTO cataloginventory_stock (stock_id, website_id, stock_name) VALUES ('1', '1', 'default');

2. php bin/magento indexer:reindex

3. php bin/magento cache:flush

But still i am facing the same issue, then I did the below steps.

1. mysqldump --single-transaction -u root -p mydb --triggers | sed -e 's/DEFINER[ ]=[ ][^]*/*/' > mydb_without_definer.sql
2. DROP DATABASE mydb;
3. create DATABASE mydb;
4. mysql -u root -p mydb < mydb_without_definer.sql
5. php bin/magento indexer:reindex
6. php bin/magento cache:flush

Thank you! Pilathraj

Make sure you have Elastic search service active status ?

service elasticsearch status

I had the same issue, I just had to execute:

php bin/magento indexer:reindex