Lenovo T500 THINKPAD and Vodafone R216H wifi modem with Debian 9 and MATE
This laptop used to automatically detect the wifi modem but refuses to do so now saying
although it still has Vodafone name and password unchanged in the parameters.
It is definitely not a matter of installing an incompatible wifi hardware but I cannot find how to "enable" wifi.
The only thing I have done regarding wifi was to adjust user settings to disable a user access to wifi to prevent the abuse of phone data allocation while the laptop was used by someone else in another place but now returned to its original place of usage.

Has anyone any advice on how to solve the problem?

Thank you for your help.

Assuming that there is no physical switch on the modem that may be off, then you should look in your network manager to re enable wifi, (you don't say which network manager you are using, so can't give a specific answer).

You said you changed the settings to prevent someone from using wifi. Change those settings back to what they were.

There is a physical switch to disable wifi on some laptops. Make sure that you have not thrown it by accident. Run rfkill as superuser or sudo to see if it is blocked there, and unblock if needed. Run ifconfig (as su ) to see what the name of your wifi device is and to see if it is up and to make it up if it isn't. Make sure whatever you are using to configure wifi is using that correct device name. This a way to troubleshoot on slack. If systemd makes this advice outdated on debian, maybe someone else can correct me.

Some of those have to have bluetooth enabled in bios also ??
Edit, dang didn't know it was a usb gizmo. Thought it was wifi.

The command lspci issued in a terminal should reveal which wireless chipset your computer contains. You may have to issue the command as root.

^ not in this case.
It's one of those 4G modems that create a wifi hotspot; completely detached from the computer (except charging via USB):
https://wirelessgear.com.au/vodafone...g-r216h-modem/

Since all it does is create a wifi hotspot, troubleshooting is limited to
a) your network manager's wifi settings
b) the modem's settings (encryption, SSID name etc.)

Hi.

Co-incidentally, I was going to create this exact thread. Here is some more info. Please help.

1. My laptop has a built-in Wifi-Bluetooth thingy (RTL8723BE), which is defective, due to it being so many years old. Sometimes my kernel detects it, and sometimes it doesn't. So, it's unreliable. Therefore, I got a new USB wifi receiver to replace it.

2. Everything works fine, until I close the lid of my laptop. Once I lift the lid, the NetworkManager says ''Wifi disabled by hardware switch''. And rfkill as super user gives this output,

I know that there is supposed to be a physical switch that should turn that ''Hard blocked'' to yes. But on my laptop that thing doesn't work on Linux because of some bios settings. Few ago I did my research and it seems there is no way to toggle the ''Hard blocked'', and since my internal RTL8723BE is not being used, I'm not worried. But, the external wifi-receiver is a usb device. I can remove it, I can plug it in. I am sure it is not ''Hard blocked''. Yet NetworkManager still says that ''Wifi disabled by hardware switch''.

3. I tried to restart the NetworkManager service. (I use the runit init system.)
Now, the NetworkManager gives a different error, ''Wifi is disabled'' and the checkboxes on 'Enable Networking' and 'Enable Wifi' is grayed out (not clickable).

It's fine if the BIOS is preventing my internal RTL8723BE from restarting, I want my external Wifi receiver to work. Anyone know the solution to this?

SegFault1 you need to start a new thread. Your problem even through it may be similar, the solution may be totally different, and reduces confusion for those providing answers to this thread.

Quick answer - plug in your USB dongle before starting up your computer - the system should load a driver for it, then you configure your network.

If the dongle and the internal wifi are using diffent kernel driver modules, blacklist the the kernel driver module for your internal wifi card. Most likely, if this is done, linux will act like it is not there.

I'm confused. I assume you can access this via a usb cable to get it to work but also you wish to now connect it to wifi.
You said you played with some settings. Can you create a new user and see if that new user has proper settings to make it work?

Thank you for the answers.
The laptop has wifi "Intel Corporation Ultimate N Wifi Link 5300" (no need for a dongle) which worked before with Vodafone wifi modem R216h, this modem works with my desktop and sent this message. I only have wifi Internet.
The network manager is the Gnome network manager.

The only thing I changed between the time it worked and the time it did not worked was to ensure user user2 had no access to wifi and accidentally wipe out the small wifi data allocation of user1/root. user1 was the main user defined at the time of the installation with settings not changed since the time of the OS installation (user1 having access to wifi). User1 is now the only user and has correct permissions.

Nothing I tried worked although some suggestions could not be tried without installing software (ifconfig deprecated and replaced by ip).
I decided to cheat and tried reinstalling Debian 9 but it could not communicate with the wifi network even though I position the wifi modem's antenna within 3 metres of it. Install found and used the non-free firmware iwiwifi-500 on a usb and was happy with that but then it choked on the WIFI KEY. I took screenshots of the messages supposed to have been saved in /var/log/netcfg-wpa but after rebooting, I found there was no such directory.
Issuing service network-manager restart only gives a message that the network has been disconnected.

That suggests to me that there may be a physical switch somewhere on the laptop that enables/disables wifi. I have no idea where it would be, but perhaps reading the manual for the laptop would help find it.

After some digging on the Lenovo website, I can't find a T500 manual, but for a T520 and others there is a switch at the top of the screen which controls wifi. It appears to be a slider switch, as far as I can tell from a poor .pdf image. Try sliding that switch and see if wifi is enabled.

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Unbelievable! That's what it was, a tiny slider switch. Slided it and now I got wifi. What was the logic behind having a switch for wifi is hard to figure out.