Make a copy paste answer ready because people don’t read and don’t use the search? 
Like
Please use this command while being in your ownCloud directory:
sudo -u www-data php occ file:scan --all
followed this Why does my files I put into datadir don't appear in ownCloud?
which lead me to outdated links to the 8.2 and 9.1 docs without the command that I need.
also followed this Files can be seen after rsync
and also did not find the command.
Am I missing something? @tom42