out of the blue puppetdb_fact stopped working

$ bolt plan run puppetdb_fact -t all
Starting: plan puppetdb_fact
Finished: plan puppetdb_fact in 5.48 sec
'add_facts' parameter 'facts' expects a Hash value, got Undef
  (file: /opt/puppetlabs/bolt/lib/ruby/gems/2.7.0/gems/bolt-3.27.2/modules/puppetdb_fact/plans/init.pp, line: 16, column: 5)

bolt inventory works, so puppetdb connection is fine. what gives?