Plugin not working on every URL

We’re a design agency and used the plugin for one of our clients. Every worked fine with the “content-stage” -> all Portfolio images as well as nectar slider images were fixed.
Now we want to use your plugin on our own website (same theme (Salient), same wordpress version as on our clients site) – but it’s not working. Especially the nectar slider images cause “mixed media”.
We already tried to uninstall and install the plugin but nothing worked so far.

Any advices?

Thanks for your help.

The URL of our clients page: https://www.bernhard-floeck.de/
Our URL: https://www.elevate-identity.com/

Some URLs on our page where you can see the plugin is not working:

https://www.elevate-identity.com/portfolio/ambright-leds-create/
https://www.elevate-identity.com/portfolio/trenkwalder/
https://www.elevate-identity.com/portfolio/drehmoment/
https://www.elevate-identity.com/office/

As you can see it’s not online the portfolio pages…