Connect the phone to a PC, make sure your developer options are enabled. Then, connection type must be MTP or File Transfer. Charge only does not allow USB debugging(disables the option).
This worked for me:
Try selecting the default mode as Internet connection.
Go to Settings -> Connectivity -> Default Mode -> Internet Connection.
Now enable the USB Debugging mode under Applications -> Development -> USB Debugging.
It worked for me.
You have to enable USB debugging before plugging your device in to the computer. Unplug device then try to enable USB debugging. This should work. If so, you can then plug it back into the computer and it should work
How to Enable USB Debugging for LG Optimus (LGD415). Android version 4.4.2 (KitKat)
Go to this website and download the drivers to your phone:
http://www.lg.com/us/support/mobile-support
For example, mine would be:
http://www.lg.com/us/support-mobile/lg-LGD415RD. Then click on “Software Update & Drivers”
On your phone, you need to enable USB debugging. To do so,
Go to “Settings”.
Go to “About Phone”
Go to “Software Information”
Tap “Build number” five times.
A pop-up will appear saying “You are now a developer”. Your’re not done yet.
Go back to your phone’s home page by pushing the home button.
Go to “Settings”.
Go to “Developer options”
Click the “USB debugging- Turn on debug mode when USB is connected”. A blue checkmark will appear.
(EDIT: If USB Debugging is greyed out, unplug your phone. USB Debugging should no longer be greyed out. If it is not greyed out, check the box and plug your phone into your PC.)
Unplug your phone from your PC. Then plug it back in. On the pop-up, make sure you set it to “Media Sync (MTP)”.
Now your phone will show up on an option when you want to run your app in Eclipse.
(Look for dialog box on phone and agree to allow debugging connection with your computer.)
(Also, go to Control Panel | Device Manager and make sure there are TWO entries for your phone, similar to those expanded below.)
Just ran into this on the LG Rebel LTE (LGL44VL). As other answers note, you need to change the USB connection mode to PTP. But my phone's control panels were different from stock Android and didn't have such an option.
The option was hiding in a notification that appeared when I plugged the phone in. I had to open the notification tray and tap a notification labeled
Media Device (MTP)
Tap here for more USB options
FYI My Motorola Xyboard had an "Off" icon at the top of developer options. Once I tapped that it worked.
Just ran into this issue on a current LG phone on a windows computer. Everything from developer options was enabled correctly, but wasn't able to see the device through ABD. Needed install drivers which I was able to do from the phone.
After connecting through USB and allowing the connection, I tapped the USB connection type notification and on the screen where you select the type of USB connection (MTP, PTP, etc..) I tapped the three dot icon in the top right hand corner of the screen and selected to install the PC drivers. After installing the drivers on my PC I was able to connect through ABD to debug.
I had an LG Android phone, and could not get USB to work with Windows, even after trying the following:
It DOES show the phone as charging via USB (so the plug must be OK), but it does not show up under 'This PC' in Windows File Explorer as a Device/Drive.. grrr.
Turns out that not all USB cables are the same — some USB cable manufacturers only make their cable with 2wires instead of 4wires, so that they will charge, but not pass data through the cable — so if software solutions do not appear to be working, try changing the USB cable (!).
im writing this here so that maybe someone else doesnt have to waste half an hour figuring out that some USB cable manufacturer doesnt include all 4 wires in their USB cables... grrr.
After countless attempts, I found the following quote:
If you are using My KNOX, you cannot enable USB debugging mode while the container is installed. Unfortunately, you have to root your device ... - continue reading
Furthermore make sure:
I switched to another device without KNOX (not rooted as well) to save time. Maybe this quote will save someone some time. It was the only explanation to me in this case.
Cheers!
Unplug your phone from the your computer, then choose PC Software as PC Connection Type. Then go into Developer Options and select USB Debugging
Unplug your phone from the PC and go to develop options and now here you can enable USB debugging. if you connect USB and try to enable debugging it will not enable and follow TMacGyver is right it works for me using choose PC connection.
To enable USB debbuging you have to enable developer option
Now if you have shaded usb debbuging and it is not turning on
Now you can enjoy your sharing ...
I have a feeling that if you have a corporate phone, your corporation IT might also be blocking USB Debugging. I've tried all the different connection modes and the USB Debugging option remains firmly greyed out.
I'm trying to get in to enable the BATTERY_STATS for GSam Monitor Pro, but I think it's disable through the Airwatch MDM software my company makes me use. They pay for it so I guess I'm stuck.
Source: Stackoverflow.com