"Does not return" or "Does not returns"

Question

Context: Software Documentation/Error Messages

Lets say we are talking about the capabilities, or lack thereof, of a non human entity (computer/machine) to do something, in this case returning something.

According to this page under Negative Sentences in the Past Simple Tense:

Negative sentences with do not, does not and did not

When creating negative sentences, we usually use shortened forms: don’t, doesn’t and didn’t together with the base form of the verb.

Note: Save the long forms (do not, does not and did not) for when you want to create emphasis. When speaking, you would put an accent on the ‘not’.

The question arise when adding a message to indicate the machine is not conforming to certain standard; I am writing the following message:

"The 'Entity' does not returns XYZ"

1. is that message grammatically correct? - Considering that it wants to emphasize the perpetually continue lack of capabilities of the 'Entity' to return a thing
2. Should the correct spelling be "The 'Entity' does not return XYZ"? - Without the s at the end of return
3. If both are correct, which one would be preferred or "more correct" when notifying a user about the "state/capabilities of the system"?

As an example of the use case consider wanting to emphatically clarify that a vending provides no change

Answer 1

In software documentation I've written you would either say

The 'Entity' does not return XYZ". - as in your point 2.

or

The 'Entity' returns XYZ". - which is the opposite case.

"Does not returns" is grammatically incorrect.
In my opinion The 'Entity' doesn't return XYZ" carries the same weight and meaning. The use of contracted forms makes no difference. Some might claim that the more formal the writing, say the user's manual, should use the full form and less formal, such as the embedded comments (you do insert copious comments, don't you? 😁) can use the contracted forms.