Resolved.
I reinstalled the WAPT agent; the password requested on the first attempt also had to be the server password and not a Kerberos identifier.

Sorry, I forgot to mention that.
Server OS: CentOS 7
WAPT Version: 1.5.26
Developer workstation OS: Windows 10

Hello,

I followed the Kerberos setup instructions correctly, I can register my workstations via waptdeploy using GPO, etc.

However, when I try to upload a previously created package, it fails:

c:\waptdev>wapt-get upload-package chk-microsoft-visio-2016_16.0.4266.1001-0_x64.wapt
Uploading packages to ...