@Tor-Suneson Check if the yellow play area bar at the top of your project isn't collapsed into a single point, which is a bug and can happen from time to time. You then need to change the view layout with the magnifying glass icon in the bottom right corner of the audio track area to reset the bar length.

Next check your audio driver settings inside Music Makers program settings and that the driver is configured correctly. Direct Sound should work fine on most hardware but will not give you live monitoring. ASIO drivers are recommended for all features. Magix comes with Magix Low Latency ASIO that needs to be configured by clicking on the Advanced button. You need to enable your audio inputs and outputs.

You can also use other ASIO drivers like ASIO4All (which is nearly identical to Magix Low Latency), FL Studio ASIO (install the free demo version of FL Studio), Steinberg Generic ASIO (install the free Wavelab demo) or a USB audio interface with its own ASIO driver (this is the best option but costs additional money).