Pymodbus not finding 'grouped' addresses on device

I am working on a project in which I'm using Pymodbus to connect to an industrial fan system. I am able to read some addresses on this fan, but not others. The fan's instruction booklet I am working with puts the addresses into "parameter groups", as follows:

Grouping	Description
Group 00	Basic parameters
Group 01	V/F pattern selections and setup
Group 02	Motor parameters
Group 03	Multi function digital Inputs/Outputs
...
Group 15	PLC monitoring function

For each grouping (1-15) above, there are then more specific addresses provided in later pages of the manual. For example, for Group 00, above, there are address entries specified as below:

Group-address	Description	Range
00-00	Control Mode Selection	0: V/F Mode, 1: Vector mode
00-02	Main run command.	0: Keypad, 1:Communication, 2: PLC
...
00-20.	Jog deceleration time.	~0.1-3600.0

I am able to access and print the above addresses (for the case of the grouping of '00') with the following Python script:

from pymodbus.client.sync import ModbusSerialClient as ModbusClient    
modbus_conn = ModbusClient(method='rtu', port="/dev/tty.usbserial-AQ00BYCR",baudrate=38400,parity = 'O')
modbus_conn.connect()
print(modbus_conn.read_holding_registers(0,20,unit=1).registers[0])

The problem, however, is that I cannot access the higher groupings ('01' -> '15'). For example, if I try to access any address higher than 20 with the above script, I get a "no registers there" error. I'm assuming this is because I am locked into sampling the first grouping ('00') with my script.

I explored the idea that groupings specify different address starting points, so I tested to see whether '01', for example, meant an address starting at the location of '100', as below:

modbus_conn.read_holding_registers(100,5,unit=1).registers[0]

but this turned out not to work (since I again got 'no register exists there' errors).

What am I doing wrong?

What am I missing?

Does anyone out there know how to access addresses that are grouped in the above way? This is the first time I've seen this, and I am stumped.

Thank you in advance!

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