Error claiming core through stand alone AP

Core arrived in post today - excited to get it online. The first stage of setting up the core on my local wi-fi seemed to go OK when the Android app led to the core’s LED changing from flashing blue to green just as I entered the SSID and password in the app. However it stayed in a cycle of flashing green for around 20 seconds, then a brief flash of white, forever. Network setup is a Ubiquiti 2.4G wireless access point separate to the home router, set to channel 3, WEP security, working fine for years with no recent changes. All home PC’s / laptops / phones work through this AP.
I solved the problem (for now) by enabling the routers inbuilt wifi (2.4G, different channel, new SSID, WPA security). Connected phone to this, factory reset the core, and all progressed fine - now happily blinking LEDs and loading sketches etc.
I plan to deploy some cores to remote friends and neighbours for a little project and need it to “just work” - any guesses on what may have caused my problem on what I thought was a pretty standard home Internet set-up?

Best I could think of was maybe some port blocking in the access point (which is almost factory defaults - nothing clever) but this seems a little unlikely. Any ideas? (Thanks in advance).

EDIT Another possible- would the original AP being set to ‘N’ only, but the router wifi being mixed be an issue? If so isn’t this (common, modern) scenario going to cause a lot of issues in ‘consumer friendly’ set-up?

Hello @Warwick yes that can be an issue as the chip on the spark core is a CC3000 and can only connect to IEEE 802.11 b/g ( 2.4GHz) therefore some routers posse this issue and cant connect without changing the settings. Most routers support b/g but sometimes don’t come configuration out of the box enabling b/g and only running /n.

WIKI on CC3000

That could be a real problem for consumer products. Asking Joe public to log in to and reconfigure his router to get his internet enabled cat bowl working is hardly use friendly!