pretest, error on Win 8.1

[Keks Dose]

Hi!

Full install of pretest today, succesfull, I can compile *.tex files. I called the installer-tl-...bat as admin.

When I open "cmd" as admin, the command "tlmgr --gui" produces an error:

========================

Cannot load Tk, that should not happen as we ship it!
How did you start tlmgrgui??
(Error message: Can't locate Tk.pm in @INC (you may need to install
the Tk module) (@INC contains:
C:/ texlive/2019/texmf-dist/scripts/ texlive C:/ texlive/2019/tlpkg
C:\ texlive\2019\tlpkg\ tlperl\ lib C:/ texlive/2019/tlpkg/ tlperl/site/lib
C:/ texlive/2019/tlpkg/ tlperl/ lib) at
C:\ texlive\2019\texmf-dist\ scripts\ texlive\ tlmgr.plline 5093.
)

========================

I can open tlmgr gui simply using the start menu of windows, folder "TeX Live 2019" and open the item "TeX Live Manger" as admin. That works.

I have no idea why I get this error message. There is an perl installation on the machine, but in the PATH variable the very first item is "C:\texlive\2019\bin\win32". I did not reboot, though.

Regards,

Alexander