How to fix "Invalid OTP" error during setup
In order to ensure the utmost level of security, the web-based portion of the setup process must be completed within 5 minutes; taking longer than that will result in an "Invalid OTP" error, and the setup will fail.
If that happens there are 2 possible ways to fix the situation.
Fully uninstall Syncplify Server! v6 from the Windows Control Panel or, if it's Linux, using the setup CLI, then reinstall the software anew (fresh, from scratch).
Run a terminal (cmd.exe, PowerShell, or any terminal/shell in Linux), then change directory into the folder where the software is installed, and type the following:
For Windows (as Administrator):
sudo ./ss6-webrest genssc