CTL-Y no longer works

Question

Suddenly the highlighting color, when copying changed from gray to yellow. CTL-Y no longer works, When I try it I get: Symbol's function definition is void: x-cut-buffer-or-selection-value.

My .emacs file

(setq
  time-stamp-active t          ; do enable time-stamps
  time-stamp-line-limit 10     ; check first 10 buffer lines for Time-stamp:
  time-stamp-format "%04y-%02m-%02d %02H:%02M:%02S (%u)") ; date format)
(add-hook 'before-save-hook' time-stamp)
(add-hook 'isearch-mode-hook
   (lambda ()
     (define-key isearch-mode-map    "\C-y" 'isearch-yank-line)
     (define-key isearch-mode-map "\M-s\C-e" 'isearch-yank-kill)
    ))
(setq isearch-mode-hook
      '(lambda nil
     (define-key isearch-mode-map "\C-y"   'isearch-yank-line)
     (define-key isearch-mode-map "\C-f"   'isearch-repeat-forward)
     (define-key isearch-mode-map "\C-t"    'isearch-toggle-regexp)))
(setq x-select-enable-clipboard t)
(setq interprogram-paste-function 'x-cut-buffer-or-selection-value)
(set-face-attribute 'default nil :font "monospace-20")
(setq lpr-command "gtklp")
(setq buffers-menu-max-size nil)
(setq ps-lpr-command "gtklp")
(setq web-mode-content-types-alist '(("jsx" . "\\.js[x]?\\'")))
(setq css-electric-keys nil)
(add-hook 'MAJORMODE-mode-hook 'my-MAJORMODE-mode-hook)
(defun my-MAJORMODE-mode-hook ()
  (ELECTRICMODE-mode 0))
(defun undo-all ()
  "Undo all edits."

Answer 1

Replace x-cut-buffer-or-selection-value with x-get-selection-value. The former was an old name for the latter. You probably upgraded Emacs to a more recent release, which no longer supports the old name of the function.