Connects to 5 but not to 2.4

I have all my HomeKit devices connected to 2.4, no issues. On my router, both 2.4 and 5 have the same configuration. They are named the same except for the end, where I added 5G to the 5g wifi.
The Rachio 3 connect to the 5G, but will not connect to the 2.4.
I get an error.
Any ideas?

Why not use the same SSID for both radios? Makes managing all devices easier and devices can switch as needed. I’m not sure how that would affect your HomeKit setup. The 5ghz bands are typically a strong connection for compatible devices closer to the router, plus faster, while 2.4ghz allows for further connectivity range. I’m not sure why your Rachio won’t connect directly to your 2.4 though. I’ve had some devices over the years with the same issue, would connect to one band and not the other, and only fix I found was to use the same SSID for each band. Not sure why.