M/B M571-H not detect pnp int. modem

I test PC100 MotherBoard M571-H with pnp internal modem USRobotics 56K OEM PCI Voice SoftModem
but CMOS checksum cannot auto detect.
Computer Specification CPU Pentium233MMX,SDRam 16MB*2,VGA&Sound on Board,Hdd. 3.2 GB,4 PCI(v2.1),2 ISA,lastest bios upgrade,Windows98SE, Driver Sis5597/5598.I try that modem with COMPAQ EP6400J it’s working.I don’t understand why cmos not detect the internal modem.