I have had the same issue with my ASUS router (see sig for exact model number)

A web site comes up wanting a user name and password for which I can't remember what it is because I set this up 5 years ago. (I may have never made one)

The key to getting through the issue is to just keep entering a wrong password (pretty sure I just leave it blank) 3 or 4 times in a row (or more). Eventually an iPhone driven message box will come up asking you if you'd like to use this network "without the internet", select that and the phone will then actually connect to the router and all is good. Also, this should not happen again for that phone once you get it working. As long as they don't delete that Network connection from their phone.

I very rarely have anyone using QMIX with my system, so I don't run into this often. I do have an extra phone in case I have someone who wants it and knows what they're doing (rare) and I have already got it connected properly.

If someone has their own phone to connect, I will usually ask them to let me dork with it for a while (because it's such a PITA I don't want them to have to deal with) and like I said I will just keep trying until I get that button/message in red saying "Use Without Internet", tap it, then all is good. I never actually log into the router like it seems to want you to do.

I am not sure how to actually change the settings so that this doesn't happen anymore, whether that be in the router or in the phone (not sure). But I do seem to be able to get around it every time. (After a bit of frustration I'll admit)

Same deal with iPads.

Steve