Laptop Running 18.3 Mate Can’t “See” or Connect to WiFi Network with First Reboot

[TomKG]

I am a beginner trying to convert a 9 year old Dell XPS M1330 laptop (with a Broadcom WiFi mini-card) to a LINUX learning tool for myself. I downloaded and was about to try Mint 18.2, when I read that 18.3 was available. Thinking newer is better, I proceeded with the Mate 64-bit version. The installation went smoothly and, after selecting the recommended bcmw wireless card driver and the Intel microcode, I was online. The system found my network, loaded a functional printer driver and operated like most new machines…. right up until I shut it down. Since then, it’s been unable to see or connect to any wireless network.
I’ve tried rebooting the system from the USB stick, running “sudo service network-manager restart”, installing the network manager update, loading the 4.10 kernel and disabling WiFi power management, all without improvement. Running “rfkill list” revealed neither software nor hardware block. The only thing that helped was deleting the Mint file from the USB memory stick and reloading it from an ISO file stored on another PC. Unfortunately, this only worked once. Upon a reboot, the PC with the persistent live USB copy, forgot how to find a wireless network, in spite of retaining my SSID and password. Internet is only available via Ethernet connection.
I’d be grateful for any suggestions for resolving this mystery.