BI iOS app won't connect on 2.4ghz network

[rsg]

I have two wireless SSIDs on my network--one that's 5ghz and the other is 2.4ghz (my garage has poor wifi coverage and only the 2.4 works there).
Blue Iris iOS app will not connect when my phone is connected to the 2.4 network: "unable to make connection". Works fine when I use the 5ghz or when the phone is connected to my Microcell or any external cellular/wifi network.
This poses a problem when I am trying to quickly see who's at the front door.

 

[TonyR]

More info needed:
1) Do any other devices connect OK on the 2.4 GHz network?
2) In the wireless router / access point, is the 'Channel Width' for the 2.4 GHz network set for 20, 40 or Auto?
3) What make & model is your wireless router / access point?