Could be the 5268's band steering (where the use of 2.4 and 5 are optimized) is confusing your 2.4 devices. So get into your gateway (192.168.1.254), navigate to its wifi section, and give the 2.4 and 5 different ssid/passwords. That disables the band steering and allows your 2.4 and 5 devices to access the specific radio (2.4 or 5) by its respective ssid.
*The views and opinions expressed on this forum are purely my own. Any product claim, statistic, quote, or other representation about a product or service should be verified with the manufacturer, provider, or party.