I can not access the property of a web form with Robobrowser

I'm trying to access the content of a website but for that I have to cover the zip code. When I try to access the property 'cl_postal_code' I get an error. What can be happening?

from robobrowser import RoboBrowser

browser = RoboBrowser(history=True, parser='html.parser')
browser.open('https://www.gadisline.com/')
form = browser.get_form(id="form_postalcode")

form["cl_postal_code"].value='15000'

browser.submit_form(form)
print(str(browser.parsed))