Hi @ Flórida da Graça Botelho Araújo ,

According to your description, unfortunately I cannot reproduce your problem. I want to confirm if you use and develop it in SharePoint?

Based on this error message: Refused to display 'https://xpto.pt/' in a frame because it set 'X-Frame-Options' to 'sameorigin''. Please try to do some troubleshooting:

<iframe class="xpto" src="https://xpto.pt/&embedded=true"></iframe>
2.If your application have web.config then add the following tag in web.config:
<system.webServer>
    <httpProtocol>
        <customHeaders>
            <add name="X-Frame-Options" value="ALLOW" />
        </customHeaders>
    </httpProtocol>
</system.webServer>
This will allow application to append iframe from other origin also. You can also use the following value for X-Frame-Option :
X-FRAME-OPTIONS: ALLOW-FROM https://example.com/ 
Similar issue for reference: 
Refused to display ‘url’ in a frame because it set ‘X-Frame-Options’ to ‘SAMEORIGIN’
How to fix Refused to display in a frame because it set 'X-Frame-Options' to 'sameorigin
Hope it can help you. Thanks for your understanding.
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Captura de ecrã 2023-01-11 105521.pngHello
Thanks for the repsonse. 
I have added in the web.config the setting.
However, now the error in the image below appears "Refused to display 'https:... in a frame because it set multiple 'X-Frame-Options' headers with conflicting values ('SAMEORIGIN, ALLOW'). Falling back to 'deny'."
 I have checked in webpart and in IIS and there is no SAMEORIGIN setting...where could this setting be?
 I also noticed that the behavior of the component differs by browser. In IE it says "This browser does not support inline PDFs. Please download the PDF to view it: Download PDF", in Edge it says "www.xpto.pr refused to connect".
Any suggestions?
						
I've done everything, but I'm still in trouble. 
I also followed this post [http://sadomovalex.blogspot.com/2015/12/remove-x-frame-options-sameorigin-http.html
and returns the error of the attached image... 
       Invalid 'X-Frame-Options' header encountered when loading 'https://www.xpto.pt/': '' is not a recognized directive. The header will be ignored.
1.png
Any suggestions? Thanks