Firmware, DFPlayer initializing Failed (DFPlayer not detected).

[ForrestErickson]

Describe the bug
A clear and concise description of what the bug is.
Short Summary of the expected behavior:
The factory test for the Mini MP3 Player items, 4, 5, and 6 should work.

Short Summary of the buggy behavior:
On SN: US0007 which passed a previous factory test for the Mini MP3 player on FIRMWARE_VERSION "v0.4.2.6" there is no sound and the Mini MP3 player reports not found.

Enter command: 4

[4] DF Player
initDFPlayer() called at: 129479
Initializing DFPlayer (UART2)...
InitDFPlayer, dfPlayer.available(): 0
DFPlayer not detected. Check wiring & power.
DFPlayer initializing Failed (DFPlayer not detected).
dfPlayer.available(): 1

Command 5 and 6 fail to make the speaker make any souund.

Screenshots
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Firmware description
File: FactoryTest_wMenu
Branch: (bugfix/356-firmware-factory-test-bring-up-add-flow-control-test-for-com-port)
Firmware Version: v0.4.2.6

Hardware description
Model: Krake
Serial Number: US0007