Notification/Popup Message Does Not Appear on Validation

Question

I created a custom doctype and applied a restriction for the user that cannot enter a non-negative value. I used it for field data type INT. The doctype validates the value if it is negative it shows a sound and doesn’t save/submit. The user cannot recognise the reason since it just beeps/sounds without any message or notification.

CHECKED ALREADY:

Popup-Window is allowed on web-browser. No restriction defined on web-browser or website Tried Chrome, Edge, Firefox, browsers but results are same. I would like to know why no notification appears. am I missing something or what should I do to show this message?

EXPECTATION:

I am expecting, if the value is negative then a popup message or notification should appear to notify the user that negative values are not allowed and so on.

CURRENT ENVIRONMENT:

Below is the environment I am using:

Installed Apps,

→ Frappe Framework: v15.40.6 (version-15)

→ My First Application: v0.0.1 (develop)

→ Developer Mode ON

Additionally, I have attached pictures for the reference.

BELOW IS THE BROWSER CONSOLE OUTPUT: