change iframe width css code example
Example 1: set iframe height and width by js
#IFRAME_ID {
width: 100%!important;
height: 100%!important;
}
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If still not working you can try solution from on the solutions from the link
https://stackoverflow.com/questions/819416/adjust-width-and-height-of-iframe-to-fit-with-content-in-it
Example 2: set iframe height and width
#IFRAME_ID {
width: 100%!important;
height: 100%!important;
}