An unexpected error occurred…

I got this today when trying to search for a ne plugin.

I have read a lot of threads. And i have not figured my problem out.

i tried this guide and it works: https://www.dougsparling.org/using-curl-to-test-the-wordpress-theme-and-plugin-apis/

but i still cant search the plugins from my installation.
i have tried renaming the plugins folder and mu-plugins folder.
Restartet the server.

nothing works