@Gaxel
We will do some troubleshooting first and try to figure it out.
What is the light status of the TD-W8961N when wifi disconnected?
With your computer or smart phone connected to it at that time, what is the IP address and default gateway it obtained? And can you get internet from it by ethernet connection?
Note: How to get them: https:// https://www.tp-link.com/support/faq/838/
Meanwhile, please try to access the web page and take a snapshot of the status page.
Note: How to login to the web interface: https:// https://www.tp-link.com/support/faq/114/
How do you make it back to work after it goes offline?
Furthermore, when did you buy it?
Here is an instruction you can follow to troubleshoot as well.
https:// https://www.tp-link.com/support/faq/2238/
Look forward to your reply.
Have a nice day.