hashrack wrote

What specific URL should I enter, on the phone's browser, to open up the voucher portal for phones that don't automatically open the portal?

Try to enter any website URL (http protocol only unless you enable redirecting https in portal settings).

hashrack wrote
There must be a URL that should work, regardless of what device is used.

Just tried it with an old laptop and the voucher portal: every site URL (even a non-existing one) causes the EAP to redirect the browser to this portal URL (placeholders used for sensitive MAC addresses):

http://192.168.5.15:8088/portal/entry?cid=00:17:XX:XX:XX:XX&ap=AC:84:YY:YY:YY:YY&ssid=WLAN-name&t=1571447614&rid=0&u=some-site.com%2F

where:

192.168.5.15 is the controller's IP

:8088 is the port number for Omada software controller / replace with :80 for OC200

cid is the client device's ID (MAC address)

ap is the access point's MAC address

rid is the radio ID (0 = 2.4 GHz, 1 = 5 GHz)

t is the current  time

u is the URL which triggers the redirect

Try this:

• check that the smartphone receives a valid IP via DHCP when associating with the WLAN
• ping the EAP from the phone (or enter the EAP's IP into a web browser's address field) to test basic connectivity
• make sure to have mobile data turned off ¹
• make sure phone doesn't switch to another nearby WLAN to which the phone was associated once before ¹
• then enter an URL (http://some-site.com/)
• if this doesn't work, try the URL as shown above, make sure to insert actual MAC addresses
• if this fails too, there happens some other weirdness with the phone

¹ Some »smart« phones have kind of a (not so smart or too smart, however you view this) failover mechanism: if they don't get Internet access instantly when associated to a WLAN, they automatically switch to another type of connection which is known to have worked before such as a mobile data link.