I am sad

The first step with any problem is contacting the dealer who sold you your unit.  The distributor or manufacturer is much more likely to respond quickly to a dealer complaint.  The next step up the chain is the distributor.  If this is not something bought through a dealer you a sort of stuck doing as you have--communicating with the company. 

From your sketchy description of the situation, you somehow got a diagnosis of the problem and are expecting the company to send you the parts to fix the amp.  Who made the diagnosis and who is going to do the parts replacement?  If it is someone other than yourself, you might get that person to help with the company.  Most companies do not want just anyone mucking around in their gear and will want some assurance that the repair will be done correctly and safely.  A bad repair could mean more than just the gear not working, it could be unsafe and it could expose the company to liability.  It is not your fault that the company has stopped communicating, but, perhaps you might have to re-think your plan to do the repair without sending the amp back to the manufacturer.

In your communications with the company, did they agree to sell you the module and then not follow up with any further communication?  I am a bit confused as to how the problem was diagnosed and why the company would agree to send you the parts to do your own fixing.  That is quite unusual.  Most companies don't want the customer so much as opening the equipment case and have warnings about voiding any warranty if the case is opened.  

I am also a bit confused about your switching the two modules to see if that would effect a cure.  Do the two modules have identical parts numbers?  Did the amp only fail in one channel such that a swap of modules in separate channels could confirm that the failed module was the cause?  Did the company recommend this as a diagnostic step?  Did you confirm that it was safe to do the swap?  If you did this on your own, did you practice proper grounding of yourself to prevent electrostatic discharge damage?  It is not clear the extent to which the company endorsed your plan to replace the module and then failed to follow through.

That is good news.  I hope the replacement module does the trick. Sometimes, it does take a bit of public pressure to get a company to act.  I am glad it worked out and I hope the company learned to be more responsive.