It's about a TLS/SSL certificate of the FTP server. Is it your FTP server? The certificate usually does not renew on its own. Someone from the organization that manages the server had to do it. So make them setup a procedure to notify the users. Though it is better to use a certificate signed by a trusted authority. Then the users won't have to do anything. Anyway, this is not really a WinSCP question.

Hello,

client asked us this: (winscp, ftp, sap erp, sql, file-share)

we checked the upload. (at the SAP SQL Server)
The transfer file was created, but it could not be loaded onto the FTP server because the SSL certificate was exchanged by the SENIX server. (winscp is used)
We have stored the fingerprint of the new certificate in our upload script. We have created and uploaded a new transfer file.

It would be good to know the duration of the SSL certificate so that we can react to the exchange in the future

Do you know which "SSL certificate / fingerprint" is mentioned? How can I check?
How can I avoid that it happens again?

I am sorry, I never used WinSCP personally, just filezilla client/server sometimes. (and there is sometimes also question in connection with fingerprint etc...) (but other server, other client...)

Thx, very much in advance!