apply_prep

installls the puppet agent if one is not present, but more importantly it calls up Facter to gather facts for use in compiling Puppet catalogs from

apply

blocks. So, a broken

libfacter

would halt that whole operation. Which

puppet --version

is reported on that node? All versions of Puppet that used

libfacter

are end-of-life, so an upgrade to Puppet 7 or Puppet 8 might be something to try.