for some reason Mouse.current.position.ReadValue() returns a Vector2(0,0), no matter where the mouse is located. I also already tried to create a separate MousePosition Vector2 in the InputSystem with the same result.
Any idea what the issue might be? I already searched in Google a lot but am sure it has to be something silly.
I’m not sure this is exactly the same issue, but if you think it is, vote on it.
I filed a bug report about this (some inputs receiving a value of zero when read a second time). Unity marked it as a duplicate of the following issue (linked), so I voted on that issue to be fixed. You should too if it’s causing you problems (in my case I’m postponing upgrading to newer versions of Unity and the Input System) else who knows if Unity will ever consider it important enough to be fixed.
I had a similar problem. Mouse.current.position.ReadValue() returned a Vector2(0,0), regardless of where the mouse is located. I found the reason in my case: I was using a simulated touchscreen to test simulated touch input. While the simulated touchscreen was active, the mouse was not registering any data. You can disable the simulated touchscreen and see other input data in real time by opening the Input Debugger window (Window > Analysis > Input Debugger. Look under Devices, right click a device and choose Disable Device; or double-click a device to open a window showing the input).