Josephus relates that Antonia informed Tiberius of the conspiracy of Sejanus; and hence it has been conjectured that Secundus, unwilling or unable to have an interview with the emperor, had acquainted Antonia with the plot.
Antonia informed Tiberius of the conspiracy of Sejanus. This is what josephus relates. Secundus had acquainted Antonia with the plot. This was unwilling or unable to have an interview with the emperor. This was what it has been conjectured.