Can't maximize embed youtube video in page

Hello:

I have a embed youtube video with a frame in a page. When I use this page maximize youtube button appears. It do nothing when I click it. It seems to be disabled. I have tried to add allowfullscreen  attribute in frame but when I save page changes this attribute is cleared. I use Full HTML in page.

Anyone knows what may happen?

Thanks in advance.

Fran

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Source: https://www.drupal.org/taxonomy/term/22/feed