Sorry I am not familiar with ZKTeco (attendece system). Just searched online, it seems to be a small device for tracking attendance. If you tested your DriveHQ account with FileZilla and if it works fine with FileZilla, then it means the FTP server and your account are fine. So the problem is with the device, most likely, related with how you configured the device. Could you please email us a screenshot showing how you configured the device? (We just need to know what FTP information you entered. ( e.g.: Server / IP, the FTP protocol, port, account, passive / active mode (should choose Passive mode and the FTP directory)
If the device can be managed / configured with a PC or Mac, we can help check it remotely with DriveHQ Team Anywhere. DriveHQ Team Anywhere is a remote desktop/screen sharing service. Please download DriveHQ Team Anywhere and email us your Team Anywhere Device ID and optionally password:
https://www.drivehq.com/TeamAnywhereRemoteDesktop/
We can then try to connect to your PC/Mac and check the problem remotely.
FYI, DriveHQ's FTP service requires a business subscription. If you have a free service account, the service is very limited. You can sign up for a free business trial, or email us and we can offer you 2-week free trial.