I´ve now found out that this error exist since the last update of the nextcloud extension. This error appears every hour. Along with this update of the nextcloud extension, there was also an update of bind9.
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Code:
Zend_Http_Client_Exception: Error in cURL request: Failed to connect to updates.nextcloud.com port 443 after 210 ms: Couldn't connect to server in /opt/psa/admin/plib/vendor/plesk/zf1/library/Zend/Http/Client/Adapter/Curl.php:455
Stack trace:
#0...Read more