My Mac forgets my WIFI network
Over the last 2 weeks, my Mac has been forgetting my main WIFI network. It connects to a back-up router automatically, which does not work (no internet connection). I had the Mac "forget" this back-up router, but it does not auto-join the main WIFI network. (Yes, auto-join is selected.) The main WIFI is hidden, so I need to type the WIFI router name each time and the password, every time my computer goes to sleep. Once I do this, the WIFI works, but I do not want to keep typing the router name and password, each time. Any suggestions why this is happening. I have another (older) Mac, which is working fine, using the main WIFI network, without any issues.