“Tinny and not loud enough” after a first-fit

Vignette

A patient returns dissatisfied two weeks after being fitted with new aids set to the manufacturer's default 'first-fit'. They report that speech is unclear and soft voices are still missed.

Test findings

Real-ear measurement shows the aided output falls well short of the prescription target, especially above 2 kHz.

Diagnostic question

What is the best next step?