There is no software solution. You will have to add a new multiplexer at a new address for the 9th or move 9th to a new I2C port (if available).
The multiplexormultiplexer allows 8 devices with the same address to coexist on the same I2C bus, but it does not change the I2C address of the device.
Your 9th is in conflict with the one that is currently being multiplexed. You could disable multiplexor (via control register - no channel selected) to read the 9th, but the 9th will ALWAYS conflict with all others. The multiplexormultiplexer enables SCK and SDA to one of the 8 busses.
From PCA9547 - 8-channel I2C-bus multiplexer with reset:
From: Application Note - AN262_2 PCA954X Family of I²C / SMBus Multiplexers and Switches:
Once one or several channels have been selected, the device acts as a wire, allowing the master on the upstream channel to send commands to devices on all the active downstream channels, and devices on the active downstream channels to communicate with each other and the master.
The 9th and the 1 on the selected busenabled channel will always conflict (0x60).
There is no software solution. You will have to add a new multiplexor at a new address for the 9th or move 9th toan upstream device AND a new I2C port (if available)downstream device. Effectively, 0x60 will select two devices.