It may simply be the DHCP that's the problem - the step it's hanging on is always "requesting IP address". I've tried fixed IPs and that hasn't helped. Part of the problem is that even though I bought a designated access point device instead of a generalist wifi router (and I suspect it's the same device with marginally different firmware), the configuration process to make this stuff work is completely opaque. I have no idea what I'm doing right or wrong, and every guide says something different - at this point I'm at just "give both networks the same SSID and encryption and password and hope it all works out".
Setting all APs in one network to same ESSID is exactly wbat you should do and for half-reasonable APs that works well.
Big name brand vendors will sell you APs that support some proprietary coordination mechanism between them (usually with central "wireless network controller" as separate device), but that is not required for roaming to work. Such solutions (apart from centralized management) are mostly to keep your APs from interfering with each other (which is non-issue unless you have more than three and unless they are placed in unfortunate physical locations).
