Plugin installation not possible / FTP credentials in WP-config

I have an issue with one of my WordPress installations.

When I try to install a plugin, WP asks for my FTP credentials. I entered them but neither FTPs nor FTP are working – but the credentials are 100% correct.

I opened up the wp-config.php and pasted the configuration in the file.

When I now want to install a plugin I still see the screen where the FTP data must be entered, its greyed out with the info from the WP config file but with an error text that the connection to the FTP could not be established.

Does anybody know if this is server setting or what is wrong here?

Thanks.

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