Epidemic sound plugin not installing

There's a link on the plugin's listing page to their support page: https://support.epidemicsound.com/

I'm able to install it successfully, but I'm on macOS Sequoia 15.5, and I'm using Creative Cloud desktop app 6.7.0.278

I'd try updating Creative Cloud desktop app.

There's also a current Windows bug where you may need to run Premiere Pro once as an admin before plugins will install. A fix is coming in the next Creative Cloud desktop app update. However, the people experiencing that bug aren't getting the error code you got.