changing URL to that of an add-on domain

Hi there, I am really desperate for help here. Basically, I have this client who had a site at https://www.livewirecoaching.com and decided she wanted it changed to her name https://www.clientsname.com. I contacted the hosting company and they had me put it as an add-on domain and then said to move all the files into the root directory, and then follow the instruction on WordPress Codex as to how to re-point the URL. I did all that, and it didn’t work. So I’ve been tinkering with this site for two days and I’ve had it! I desperately just need to swoop in and tell me what the heck I’m missing. The way things are right now (which is whack if you ask me) is that I can only access the dashboard via this address: https://www.livewirecoaching.com/clientsname.com/wp-login.php. So I can get in to the dashboard and then under Settings > General the WordPress URL is https://www.livewirecoaching.com/clientsname.com and the Site Address is https://www.clientsname.com. However, when I go to https://www.clientsname.com (while logged in to the dashboard) the Home page gives me a “This site is under construction, please come back soon” message and the rest of the pages give me a 404 message. I am so lost. Please help!