Network suddenly unavailable

My MacBook suddenly says that my Wi-Fi is not available, although it shows up on the list when I click on Wi-Fi. So when I go to Network Preferences>Advanced, my Wi-Fi is not on the list. If I try to click on the plus sign and add it, I get the same message that my network is not available. When I try the Assistant, it ends up saying that my network password is invalid. I can’t “forget” or edit a network or its password (which was working for years) if I can’t get it to show up on the list! All of the other devices in my home are using the Wi-Fi! What can I do? This just started happening a couple nights ago.

Sent from my iPhone