[Avid-L2] OT ish: D-Link Access Point won't connect at 2.4 GHz?

I have an old but never used D-Link Bridge/Access Point I have hooked to my existing home network.  I have an Airport Extreme that is in the default dual 2.4 and 5.0 GHz mode.  I programmed the D-link Duo Bridge/Access Point with a new network name different from the existing home wifi network.  The Access Point only works in one wife frequency at a time.  There is a slide switch to choose between 2.4 and 5.0 GHz.  On my iPhone 11 Plus I can only see it in 5.0 GHz mode.  I google and others had complained a while back that 2.4 GHz stopped working as some IOS update.

I have a 2009 iMac 24 inch with OS 10.10.5 OS.  It sees the new Access Point and will connect when it is  in 5.0 GHz mode.  The iMac sees the Access Point when it's set to 2.4 GHz but it fails to connect with an error message saying run wifi diagnostics.  On my iPhone it doesn't even see the Access Point in 2.4 GHz mode.  I was hoping this would connect to some Ring cameras but I've learned they only like 2.4 GHz.  I can't talk to the Access Point through the Apple devices in 2.4 GHz so I'm wondering if there is some setting I'm missing.  The only thing I modified in 2.4GHz mode is the bandwidth selecting 20-40 MHz auto instead of 20 MHz.  I read usually 20 is where it's set but I don't see why that would keep it from connecting.  I want to run it at 2.4 GHz to extend the range/penetration for the outside cameras.

In 5.0 GHz mode the Access Point gives me around 70 Mbps down and 11 Mbs up and it's hardwired ethernet Cat 6 into my gig switch.  I did learn that distance really effect bandwidth.  across the house I get More like 12 Mbps down and 85 Mbs up.  I had never paid any attention to this before and learned the Airport Extreme works in a dual mode and the hardware figures out which works best for a certain wifi connection between 2.4 and 5.0 GHz.  I'm sure there are newer dual band access points but I bought this about 5 or 6 years ago during a remodel and am finally getting to it thanks to Covid.  I also read something that suggested there was a way to slave a second Airport Extreme that would take on all the settings of the main Airport Extreme Router so I wouldn't have to set up a separate network with a unique name.

I'm not looking to redo the entire network with the new, is it called mesh systems?  I'd just like to set up a repeater or Access Point on the other side of the house where I already have Cat 6 run from the network switch.  I'm not much for the wifi shuffle.  ;-)

John Moore Barking Trout Productions Studio City, CA bigfish@pacbell.net