I tried to install pdf-tools under emacs 24 and Ubunt 16.04, like I did it several times succesfully.
But now I get the error messages:
Symbol's function definition is void: pdf-tools-install
PDFs are still opened with the docview mode.
When I use M-x pdf-tools-install after Downloading from Melpa I get the message "Sever build succesfully".
Any ideas what's gone wrong?