It seems that reftex only scans the file associated with the first bibliography/addbibresource command: \usepackage[backend=biber,bibencoding=utf8,url=false, isbn=false, doi=false, ...
RefTeX gives out the following error when trying to insert a citation: No valid bibliography in this document, and no default available I keep a master .bib file in ...
How do I setup RefTeX with biblatex's citation commands? In Workflow for managing references? Seamus describes a workflow with RefTeX and mentions that it wouldn't be too tricky to add \autocite ...