If the recording signal is really weak, you might not see a waveform. You can increase the track height to see if that allows you to see a waveform. You might try adjusting your hardware gain, and/or software volume to get a stronger signal for future recordings. If there's just no waveform at all, try this:
In Mixcraft, click on the File menu and select Preferences. In the General preferences, click "Delete Temporary Files," then click OK to close the Preferences dialog and re-load the project file.
If that doesn't fix the problem, please submit an Acoustica Support request.