Could be a lot of things... So, some to check in this order :
1) The signal coming from your guitar to your audio device :
- Mic recording ? Hi-Z connection ? Line via an effect board ?
- Levels set correctly ?
2) The audio device and Cubase :
- Does Cubase 'see' the former ? In other words, is there an active and dedicated ASIO driver for it used in Cubase ? This can be checked in the 'Device setup' window, 'VST Audio system' entry.
- If so, have you carefully set the input and output busses in the 'VST connections' window ?
3) In Cubase itself :
- In the Mixer, and provided that you have the full Cubase version, make sure that the Input channels are not hide (there is a little icon on the left of the mixer which looks like an arrow going in a box, for this) and check that a signal is coming at least in one. If not, there is probably a problem with the routing of the signal : check again the busses definitions in the 'VST connections' window.
- In the project window, make sure that you have an audio track selected (with, again, a correct input routing, check this in the 'Input routing' slot of the track inspector : you should be able to choose in it an input bus among all the ones previously defined in the 'VST connections' window) with the monitor button active (the round orange one with a speaker in it, in the track list) and record armed (the red button with a black circle in it).
If everything is correctly set, you now only have to hit the 'Record' button in the 'Transport' bar...
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