@Jaime7975 

I have had similar problems in the past trying to rename devices in the Deco app.  As someone with 60-70 devices on my network, having well named devices logically organized is important to me. I've found a couple of things that could be the issue:

1. Sometimes the app just doesn't register and save the data you enter.  My guess is this typically happens when your device's internet connection is poor or something goes wrong on TP-Link's servers.  This can happen when renaming, changing locations, etc.  Sometimes just forcibly closing the app, reopening it, and trying again will work.  

2. I found an issue with renaming smart devices (e.g. TP-Link Kasa smart switches & smart plugs).  The moral of the story is the Deco app wants you to add them as Smart Devices (using the '+' Symbol in top left corner of app) and doesn't always let you rename them in the Deco app.  See this post for more details: https://community.tp-link.com/us/home/forum/topic/174916?replyId=373460

Hope this helps!  If not maybe a little more specific information about which devices you're having trouble with (and which devices are working as expected) might help to know.