I have this similar problem using VS2019 vb.net. This is due to the case-sensitive in the holding register variable and class. Unless EasyModbus modify the variable name to some different, else, VB.net is not supported.
I have tried to use EasyModbus Master mode. When I try to update my holding register with the value 987005.3, the first 16bit register value = 18800 and second 16 bit register = 63445. However, since the holding register for EasyModbus only support Short (16 bit signed int), the 2nd register value was changes to -2091. Is there any way to support unsigned int16 for the register? Otherwise, how do you allow us to update the holding register with the float value 987005.3?