There was a thread previously created in relation to attempts to do a BoxSign Request from inside an iFrame. However, the thread was not updated with the resolution and final guidance for others facing the same issue (Refused to display 'https://app.box.com/' in a frame because it set 'X-Frame-Options' to 'sameorigin'.).
https://support.box.com/hc/en-us/community/posts/10465281536531-It-is-not-possible-to-use-BoxSign-in-an-iframe?input_string=Options%20for%20BoxSign%20in%20an%20iframe,
Question
Options for BoxSign Request from inside an iframe
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