Rejection QC room echo (reverberation)

I have had so much trouble with QC that I have no idea how to make it better. This is what I receive all the time and usually when I have returning clients they accept my work with no problem.

Please help me out here, this is what I always get:

Gabriel Uribe

INSTRUCTIONS

Hi, Thank you for your submission; we greatly appreciate your effort. Unfortunately, we have found the following issue(s) in your recording: 1. There is an audible room echo (reverberation) impacting your recording. Please ensure you record in an acoustically treated space. If you already have acoustic treatment, it may not be adequate. You'll find tips on acoustic treatment on our community page: https://bit.ly/2MrNsSV Please revise and resubmit so that we may proceed with the comprehensive screening of your audio. We trust our feedback will help you improve the quality of your work and achieve professional results.

Here you have some samples rejected:

https://drive.google.com/drive/folders/19k8DC3Vuz1h4ZqRGRq9aGmwycqwdRYuG?usp=sharing