Access2017 parameter goes NULL

Not sure I understand the question.   The first argument is the form name, but you imply that the form is opening.

What is it your trying to pass?   Unless you use named arguments, you need to supply all the parameters, and openargs is last.

Jim.

Make sure that your form name is in quotations -- otherwise it may appear like an undeclared variable (null):

' Use quotes around the first argument (form name)
' Example 1
docmd.openform( "argument" ) 
' Example 2
docmd.openform( "MyFormName" )

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Alternatively, declare and set a string variable for your form name, and then use the variable name without quotes:

' Example 3
Dim strFormName as string
strFormName = "MyFormName"
docmd.openform( strFormName  )

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And as a good practice you should always use Option Explicit at the top of your code modules, right under option Compare Database.  This forces you to declare all of your variables... which may help in debugging issues like this:

Option Compare Database
Option Explicit

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Give an example of DoCmd.OpenForm

And what are you testing in the OpenForm event?