When user is ordering a catalog item it is stuck at checkout page after clicking on submit and RITMs are not generated.
Check for the user if they have any "snc_read_only" role.
If a user has this role, they won't be able to insert any record and will you will see below errors in the logs.
Security restricted: access for table: sc_cart, user: <user_id>, operation: write -- from class: ReadOnlyRoleAccessHandler
DEBUG: Security restricted: access for table: sc_cart_item, user: <user_id>, operation: create -- from class: ReadOnlyRoleAccessHandler
When removing the role the user will be able to submit a catalog item without any issues.
You can also find more information in the docs below on snc_read_only role.