Transkribus.exe has been removed from the package for version 1.27.0, as it was misclassified as malware by some virus scanners.
It had to be replaced by an empty file such that the update process still works. This file is not functional as a starter anymore.

=> Use Transkribus.bat to launch the expert client

You may have to launch Transkribus.bat twice if you downloaded the package for the first time.
If the update process still doesn't work, you can re-download the complete packages from:
https://transkribus.eu/TranskribusX/releases