On Linux, ensure that the directory in which the files libIp_xfft_v9_1_bitacc_cmodel.so, libIp_floating_point_v7_0_bitacc_cmodel.so, libmpfr.so.4, and libgmp.so.11 are located is in your $LD_LIBRARY_PATH environment variable.
On Windows, ensure that the directory in which the files libIp_xfft_v9_1_bitacc_cmodel.dll, libIp_floating_point_v7_0_bitacc_cmodel.dll, libmpfr.dll, and libgmp.dll are located is either in your %PATH% environment variable, or is the directory in which you runs your executable that calls the FFT C model.