The widget classes templated with GtkBuilder don't load the types they require, leaving their users in despair and gloom:
** (run-vpn:1094459): CRITICAL **: 11:33:54.424: file properties/nm-openvpn-editor.c: line 2623 (openvpn_editor_new): should not be reached Error: .:4:2076 Invalid object type 'NMACertChooser'
Drag this one in manually.