@Rountex
Thanks for your remind, we will add the TL-WR740N/TL-WR741ND later.
Try to change the DNS server to 8.8.8.8/8.8.4.4 under network-LAN/DHCP settings page. Still the same, please provide the information listed below:
May I know who is your ISP?
What is the light status of the TL-WR740N/741ND when the connection drops out? Can you get internet from it via wired cable at that time? Please connect your device to the modem directly to do a comparison test as well.
When the network stops working, please check the IP address and default gateway with your computer connected to the modem/router separately and show me the status-details page. Instruction as below:
https://www.tp-link.com/support/faq/838/
At that time, please login to the web UI of the TL-WR740N/TL-WR741ND and take a full screenshot of the Advanced-status page; and go to advanced-system tools-system log to save and export it to us.
Besides, please follow the instruction below to do some test and tell me which case you belong to.
https://www.tp-link.com/support/faq/2237/
Good day.