Thank you to everyone who has responded.
Sorry, I didn't purposely leave out info on my laptop. I have a Dell Inspiron 7000, but I don't remember exactly which version of Windows it was, I just remember it basically forced me to upgrade to 10 and that was my last straw with Windows.
But, anyway, the way I normally connect to wi-fi is to go to the Network Manager and slide the wi-fi to on, it would then connect to one of the devices in the list that it is set to automatically connect. It already has the password stored so would not ask. But now, it just won't connect. Sometimes it wants me to accept that password and sometimes it doesn't give me the choice. I have told it to forget those devices and then added them back, but that hasn't worked either.
The other issue I'm having occurs when I'm connected by ethernet - I had never heard of localhost before I started having this issue and don't know why it wants to connect to it. For example, I am connected right now. I just opened another tab, ran a search and it worked and I was even able to go to the second page of results. But when I opened another tab, and tried to search, it said it couldn't connect to localhost. Closed that, opened another tab and tried again - and it worked. Grrrr.
I'm probably going to try what Bob466 suggested and try to reinstall Mint from a download. But in the meantime I'm still searching and trying stuff.
In case this is helpful, yesterday when I did "nmcli device status," it showed my wi-fi devices as "unavailable." I did it today and it says they are "disconnected." So one of the searches I ran a few minutes ago was for a way to connect them. And this was the result of that:
While it was trying to connect, it did have the pop-up for authentication, but still would not connect.
Dos2Unix -
1. Yes, that's correct, I can connect through the phone hotspot, but not the router. But others in the home can connect to the router with no issues.
2. It does have the localhost issue when I'm connected through ethernet, but I don't think it did while connected to the hotspot.
And here's the output of "resolvectl" -