The familiar reader knows I currently have 5 PC's (4 notebooks) and a Chromebook. (It's a long story, but my desktop, a backup, was hidden in storage while I lived in West Virginia about 6 years back, and I lost two notebooks (disabled by freak incidents) when I moved to Arizona nearly 4 years back. I bought a new one (with touchscreen and 360 degree display rotation) maybe a year plus back from a Sam's Club, but I haven't transitioned to it yet, mostly because I haven't taken the time to migrate all my applications to the new PC yet. Long story short, I somehow resurrected the 3 dead PC's back to life and they serve as backup or alternative devices. My Arizona PC remains my workhorse, and my WV PC, which replaced a notebook with a failing hard drive, is my go-to backup; it's still a sick puppy with a dead battery which I haven't replaced.
Of course, maintaining 5 PC's takes time (for example, I haven't applied the latest Microsoft patches yet to two of them). What do I do with them? Sometimes I'm doing maintenance on the workhorse PC; in other cases, I might use the backups as de facto second monitors or virtual televisions (e.g., I once had an issue with my cable TV connection)
So the context for the problem is I had booted up my go-to backup intending to use it for Internet purposes--when it gradually dawned on me I didn't have a usual WIFI connection. Not only that, but I couldn't get it to connect from the router or by manually resetting the correct password; I could see the network available, but I simply couldn't connect to it. I had two other PC's connected by WIFI, neither experiencing a functional issue.
It wasn't immediately obvious what the problem was. I did some surfing on the issue; maybe I had a hardware issue involving networking, maybe I had an obsolete driver issue, etc. I tried rebooting the PC. Could I still connect by tethering a 24' patch cable from the router to the PC? Yes, but that was small comfort. I really didn't want to reorganize the apartment to accommodate the patch cable.
At some point, I started running into connection problems with my workhorse PC. This led me to consider that maybe the issue was the router itself. So I rebooted the router. Bingo! I was now able to connect (after any usual setup) from either PC on WIFI. I can only speculate that maybe some patching had happened on the router which required a reboot.