I want to give the access to my user just to view the available quantity of all the products

We request you to please check if you have given the inventory permission to user.
please follow the below mentioned steps:

Step 1: Go to “Invite users”.

Step 2: Click on “roles and permission” >> click on three dots >> click on “Edit option”.

Step 3: “Enable the permission to view under Products and inventory. After that, Update role

Note: “You can assign roles and permissions from Web only”