Checkbox and Text Input does not work on a specific page

Hello everybody,

on a specific web page I have a problem to address elements. Like in this case below. Here the link to the page:

https://wiki.selfhtml.org/extensions/Selfhtml/frickl.php/Beispiel:HTML_input-Element1.html#view_result

On other pages I have no problem and I have no idea what to do with this? ID or NAME should work but does not.

Does anyone have an idea?
Thank you very much.

Code:

*** Settings ***
Library  SeleniumLibrary
# Resource  ../Resources/selfhtml_allgemein.robot

*** Test Cases ***

Page
    Open Browser  https://wiki.selfhtml.org/extensions/Selfhtml/frickl.php/Beispiel:HTML_input-Element1.html#view_result  edge
    Sleep  3s

Form elements
    Input Text  id:Vorname  Prenametest
    Sleep  2s
    Input Text  id:Zuname  Surnametest
    Sleep  2s
    Click Element  id:männl  # Radio Button männlich male
    Click Element  id:alter  # Checkbox über 18 above 18
    Sleep  4s

    # Verifikation Formular
    Radio Button Shold Be Set To  id=männl  # Radio Button männlich male
    Checkbox Should Be Selected  id=alter  # Checkbox über 18 above 18
    Sleep  4s
    Click Button  value:Und ab damit!
    Sleep  2s

Close Browser
    Close Browser

It is the usual reason. Element you are trying to access are in the frame, iframe in this case.

With Selenium Library do this
Select Frame xpath://div[@id="view_result"]//iframe

Thank you very much, that worked.