Check that the serial port speed parameters match the factory specifications of the MGE unit (typically 2400 or 9600 baud rate, depending on the exact generation of the 1000C internal logic board).
From old MGE distribution:
If you are deploying the Pulsar Extreme 1000c on modern 64-bit Windows, Linux, or a macOS server, the original software zip may experience installation errors due to OS aging. The most reliable, modern alternative is utilizing the open-source suite. Drivers Mge Ups Pulsar Extreme 1000c Software Zip