@AnnaVA 

Anna,

I found two instances where you contacted support.  The first is where you called in.  I did not find any issue with how support handled the call, although i can only go off their notes.  Although troubleshooting was pointing to your router blocking the extender from working, they did approve a precautionary RMA.  The 2nd contact was via chat when you were having issues registering your product.  Chat is on a diffrent case system so the agent did not understand you have already contacted support.  Once you explained that they should have reviewed the record.  I have informed the local supervisor to coach the agents on this.  Also i do see that they did ask the same question a few times leading to you being upset.  

For the issue at hand it does appear the overall issue in registration was with your email address domain.  I attempted to register it as you would and did get an error.  I was able however to link it to your account another way and you can not complete The RMA has been approved and you can log back into the portal for completion of the RMA

Here area few FAQs that will help you

how to submit for a replacement:  https://www.tp-link.com/us/faq-2358.html

Shipping methods explained:  https://www.tp-link.com/us/faq-2357.html

Best Regards