Tried to create new orders for customers from admin panel, but it's not working. Ordering from storefront is working well. Nothing related in log files. Does anyone have idea about what's going on? Many thanks.
Having similar issue. I can't add product to admin order. After some searching I found is related to Session size.
Using the below command solve the issue
php bin/magento config:set system/security/max_session_size_admin 0
Hope it helps