Edits does not match with the originals

I am working on an audiobook project.
My client gave me the original recording a month ago. While editing I found a few lines that need replacements.
They have recorded those lines and sent them to me(with the same settings and mic position). However, the edits that they sent now do not match with the originals that were sent to me earlier.
The new recordings sound more bassy.
Has anyone faced a similar issue?
Any help is highly appreciated.

This is a common problem when using recordings made at different times.

In sound studios it is common to take notes about the room, microphone, microphone placement,… so that the recording environment can be replicated as closely as possible. Even then, there are likely to be differences in the performers voice - professional voice artists are able to minimise these differences.

The most important step, is to record all parts with the same equipment, in the same room, with the same microphone and performer positions, and for the performer to hit the same energy and feel. Beyond that, the main tool for correcting differences is to use an “Equalization effect” (Audacity has a “Graphic EQ” and a “Filer Curve EQ”: Graphic EQ - Audacity Manual and Filter Curve EQ - Audacity Manual)

The “Plot Spectrum” tool can be useful for visualising the differences in frequency content: Plot Spectrum - Audacity Manual

If the recordings sound very different, then it will probably not be possible to make them match exactly, so you will need to either just get it as close as you can, or ask the voice artist to re-record.