Okay, what happens if you de-activate all of the test steps but just impersonate, open the form, and then set the 'Assigned to' field.  Does it set successfully?

Yes. That runs normally with only that 3 steps impersonate/open form/set value to assigned to

I removed the "save" step but thats is the test I want to test if after click on Save button the form will be saved and then the state move to "In progress" and that validation is not working the sequence of steps

1- add values on the form

2- add assigned to value

3- click on save button

4- form will be saved and the state move to "in progress"

That is the sequence I want to test

There are several 'Save' buttons you can choose from for your UI action click.  You need to choose the 'Insert' context menu version for the first save you're doing, then choose the 'Update' context menu version for the second save you're doing.  Can you verify you've got the correct UI action selected?