If you have added a WIDGET to any cms static block or cms Page and it is not visible on front-end, Don't worry just check your url_rewrite table in database, the Category or Product ID you have passed with the WIDGET it must exist in the url_rewrite table, if category or product id doesn't exist in table you can regenerate that category or product URL, once url will be regenerated and entry will added to the url_rewrite table, your widget will be visible on frontend.
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