The way I usually solve this problem is by directly navigating to the address of the router.

1. option + click on the wifi icon in your menu bar. Look for the line that says Router: followed by a set of numbers. In a majority of cases, this will be 192.168.1.1

2. In your web browser, navigate to http:// followed by the IP address from step 1. So in the most common case, I would go to http://192.168.1.1

For me, this works every time. It doesn't happen so much on more recent versions of macOS, but was common for me in Mavericks and earlier

I used to frequently run into this problem in older versions of macOS, such as Mavericks. I always worked around it by navigating directly to the address of the wifi router.

1. option + click on the wifi icon in your menu bar, and look for the line that says Router: followed by an IP address (a series of dots and numbers). In a majority of cases, the address will be 192.168.1.1

2. In your web browser, navigate to http:// followed by the IP address from step 1. So in the most common case, I would navigate to http://192.168.1.1