Evidently, your document has 'filling in forms' protection applied. If it's not password protected, you can remove the 'filling in forms' protection, but then the rest of the form might not work as intended.

PS: Please attach images, etc. directly to your post (at a suitable size) instead of linking to a 3rd-party site. I have edited your post accordingly.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]