By default, Wordpress optimises content entered in the text-section of the editor.
Unfortunately, this optimisation changes the Publitas embed code. This often causes the embed to not work as intended.
Ensure your embedded publication works with the following steps:
Click here to download/install the Raw HTML plugin.
Follow the instructions on this page to install and activate the plugin.
With the plugin installed & active, add your embed code in the text-mode of Wordpress. Make sure to place it between [raw] and [/raw] tags. These tags will prevent Wordpress' optimisation from breaking your embed code.
Note: Always be careful with installing and activating plugins on your Wordpress website. After testing the solution above, please check your website's other pages are still working as intended.