Medeli M5 can't work properly with FL Studio

Hello, just a question from my husband: we have synthesizer Medeli M5, we connected it to the computer as midi, via FL Studio. We can play only 1-3 minutes, then the keys produce no sound. The synthesizer works ok, FL works ok, there's sound from the computer keyboard, but there's no sound from the synthesizer. Have you ever encountered the similar problem?