Manifest Refresh fails with Invalid credentials or RestClient::BadRequest: 400 Bad Request error in Red Hat Satellite 6

Issue

• The Manifest refresh task is not getting completed successfully and failing with the following error.

  2020-04-10T10:46:41 [I|app|] Current user set to admin (admin)
  2020-04-10T10:46:42 [E|bac|] Invalid credentials. (Katello::Errors::CandlepinError) /opt/theforeman/tfm/root/usr/share/gems/gems/katello-3.10.0.59/app/lib/actions/middleware/propagate_candlepin_errors.rb:21:in `rescue in propagate_candlepin_errors'
  /opt/theforeman/tfm/root/usr/share/gems/gems/katello-3.10.0.59/app/lib/actions/middleware/propagate_candlepin_errors.rb:18:in `propagate_candlepin_errors'
  /opt/theforeman/tfm/root/usr/share/gems/gems/katello-3.10.0.59/app/lib/actions/middleware/propagate_candlepin_errors.rb:9:in `run'
  /opt/theforeman/tfm/root/usr/share/gems/gems/dynflow-1.1.6.1/lib/dynflow/middleware/stack.rb:22:in `call'
  /opt/theforeman/tfm/root/usr/share/gems/gems/dynflow-1.1.6.1/lib/dynflow/middleware/stack.rb:26:in `pass'
  /opt/theforeman/tfm/root/usr/share/gems/gems/dynflow-1.1.6.1/lib/dynflow/middleware.rb:18:in `pass'
  

• In some scenarios, when navigating to GUI --> Content --> Subscriptions or performing Manifest Refresh the following error is being displayed.

  RestClient::BadRequest: 400 Bad Request