Placing order in Admin for customer does not work after upgrading to Magento 2.4.3-p1

Question

After upgrading my staging from Magento 2.4.3. to 2.4.3-p1 I am not able to place an order in the Admin for a customer. Also reordering an existing order from Admin is not possible. I can on the other hand work around by using the option "log in as customer" and place an order on the frontend. Re ordering also works as expected on the frontend.

Steps to reproduce order for customer in Admin: Customers -> Edit -> Create Order -> Add Products -> Add Selected Products to Order Above results in No product is added and the button "Add Products" disappears.

Steps to reproduce reorder: Orders -> View -> Reorder Above steps redirects to customer selection instead of reordering the product (which is in stock)

Am I the only one having this problem? Thanks for your input.

Solution:
On a hunch I ran compile again. This did not solve the issue. After this I ran the following command:

bin/magento config:set system/security/max_session_size_admin 512000

which did the trick. I found this solution on: Upgrade to magento 2.4.3 - Backend is very slow

The backend on the staging was slow not very slow but my on my live site it was when I upgraded to 2.4.3 a month ago.

Answer 1

Hit given below command

php bin/magento config:set system/security/max_session_size_admin 512000

and after that hit these commands

php bin/magento setup:static-content:deploy -f;
php bin/magento indexer:reindex;
php bin/magento c:f;
sudo chmod -R 777 generated/ var/ pub/ var/

I hope it is working for you.