broken tex.el

[Haines Brown]

I upgraded my operating system (devuan fork of debian) on new hardwre. 
I copied over the 2020 emacs configuration files and installed
LaTeX 3.141592653-2.6-1.40.23 (TeX Live 2021).

But when I open a .tex file in emacs it remains in its Fundamental 
major mode. If I switch manually to the TeX mode I get the error:

  Autoloading file /home/haines/.emacs.d/elisp/tex.el failed to 
  define function TeX-tex-mode

I have no expertise, but this suggests I need to add a statement to
my tex.el file that I didn't need before.

This file starts":

  (defun reload () "Reloads .emacs interactively."
  (interactive)
  (load "~/.emacs"))

  (custom-set-variables
    '(LaTeX-command "latex -synctex=1")
    '(TeX-PDF-mode t)
    '(TeX-command-list
      (quote
    (("TeX" "%(PDF)%(tex) %`%S%(PDFout)%(mode)%' %t" TeX-run-TeX nil
     (plain-tex-mode texinfo-mode ams-tex-mode)
     :help "Run plain TeX")
    ("LaTeX" "%`%l%(mode)%' %t" TeX-run-TeX nil
     (latex-mode doctex-mode)
     :help "Run LaTeX")
    ...'
   
No reference in it to TeX-tex-mode




-- 
Haines Brown