After some trial and error, the previous post was correct. The new TP-Link router is tri-band and the default for all IP's is to search the best connection on all three bands (2.4, 5, 6 GHz). The solution is found in the TP-Link phone app in the Clients listing, touch the device name in the list, then menu Connection Preference and select the 2.4 GHz option (Auto is default). Touch on the Save menu option.