Your Strato SFTP settings have nothing to do with it. You are not connecting to your Strato server over SFTP.
The update to Joomla 5.4.0 also does not have anything to do with it. Joomla has no say on outgoing SFTP connections. The only thing that has control over that is PHP itself.
This problem actually does not come from our software. This is actually PHP on your server (Strato) saying it's unable to access your Synology drive over SFTP. See https://stackoverflow.com/questions/61257397/ssh2-connect-error-starting-up-ssh-connection-43-failed-getting-banner Basically, it's telling you that your Synology server is set up incorrectly, or at the very least PHP (therefore, libssh2 which is used by PHP for SFTP connections) cannot access your Synology server over SFTP.
Is it possible that around the same time you made any changes to Synology and/or your dynamic DNS, or Strato made changes to DNS resolution? Did you make any changes in port forwarding on your network side (where your Synology NAS is installed)?
Nicholas K. Dionysopoulos
Lead Developer and Director
🇬🇷Greek: native 🇬🇧English: excellent 🇫🇷French: basic • 🕐 My time zone is Europe / Athens
Please keep in mind my timezone and cultural differences when reading my replies. Thank you!
