If your widget is not displaying you should check the following points:

Status of the account - if account is not confirmed the widget will not display. If your account is unconfirmed please contact us (support@callpage.io).

Trusted domains (Widgets >> Edit widget settings (pencil icon) >> Installaiton >> Trusted domains). Trusted domain should be the same as the address of the website.

CallPage code - make sure you have pasted the code correctly. In most of cases it should be right before closing tag </body> in footer section.