If a child node keeps losing connectivity to the network, try the following:

• The child node may be too far from another node; try moving the child node closer. Learn more about signal strength in the Linksys Now web interface. 
• If you have several child nodes in the network, try rebooting the Linksys parent router that is connected to the modem.
• Do you have any specific WiFi features turned on, such as MLO, DFS, or MAC filtering? Try turning off one feature at a time to isolate the issue. To disable these features, check this article.