I understand you are experiencing issues with your A40. Here are a few steps you can take to attempt to remedy the issues.
Test out the headset by itself on an alternate device. You can either test it out on a PC using the included PC splitter that splits the single jack on the headset to microphone in and speaker out jacks or you can hook up the headset directly to any smartphone.
Test out the headset and MixAmp on an alternate PC or gaming console.
Test out an alternate headset with your MixAmp.
Please let us know if the issue is isolated specifically to the MixAmp or headset by running through each step above.
If these steps did not alleviate the issues you were experiencing, please go to the link below and submit a case. Let your agent know all the steps you tried and the outcome of your troubleshooting. It will help speed the resolution of your case!
Support Channel: https://www.astrogaming.com/contact/