Our client cannot create course flow certificates. User account is LMS site collection admin and can create course flows. When trying to upload a new .jpeg certificate to course flow certificate template type, client receives an open document prompt. When they click OK they receive another message saying document could not be created.
Reported behaviour is changed when content type for Course Flow Certificate Template is changed (see docs in attachments for how to check needed settings). So perform check Library settings->click in Content types section on Course Flow Certificate template->then Advanced settings and link to Document Template.