Windows 10 Mobile never remembers WiFi password anymore after reset

[Anthony Tosie Veteran]

I use my Lumia 1520 as a mini tablet, but now it's no longer remembering my WiFi password after I had to change the password. I tried going in and forgetting the WiFi network in settings, but even after I delete it and re-add it, the password won't stick. So I'm constantly getting a "Password required for [WiFi Network]" prompt every time I turn the screen on.

 

Any idea how to fix it? I know this has happened to me before, but I think the only way I got around it was by upgrading to the next version of the Windows 10 Mobile Insider Preview, which obviously isn't an option now.