Please check that you are eligible for free upgrade. Check your Support Expires date at Help - Register box in your Server UI.
Current release dates are December 19 2022 for Mail Server,
and February 21 2021 for FTP Server.
If the release was built before your support expiry date, you should not encounter any problems.
If your support has expired, but you still install current version, the following will happen:
Mail Server will accept connections only on Primary SMTP,
so no incoming mail will be lost, while you are working on resolving the issue;
FTP Server will not accept any connections.
Resulution: either log in to your account and extend your support, or revert back,
download one of the old versions. Make sure that build date is lesser than your
support expiry date.