LG G3 not being recognised, USB not transferring files

I'm hoping someone can help. I have an LG G3 phone and is factory unlocked and running Lollipop 5.0. When I first got the phone (second hand), I was able to connect the phone via USB to my PC and was able to transfer files back and fore no problem. Until about 3 weeks ago, I am now unable to do this. The PC won't recognise the phone at all, all the USB connection does is charge the phone and I can see no option to get the phone to change to file transfer mode.

I had a look at Storage in the settings menu and I don't have the three dots that some people have spoke about. I have factory reset the phone and this hasn't fixed it.

I have tried using a different USB cable, this was the same. The drivers are installed (phone was recognized before). I have also tried the LG Suite, again same result. I also had a look in Device Manager for ACER something or other and this wasn't there.

I am currently having to use Bluetooth to transfer files back and fore to my PC and this is a bit slow. I'm assuming that an update LG have done has somehow broke the USB settings. I am also unable to root the phone (tried this before the USB stopped working and nothing worked) and possibly go back to KitKat 4.4.2 to even try that.

My phone has software version V20u-EUR-XX, Kernel Version 3.4.0 and build number LRX21R.A1439960697. There is no update available for my phone in the Software Update center.

After quite a bit of searching, it seems that this is a common issue but I have not found a solution to this. Can anyone help? Is there any firmware or software that I can try?

Thanks.

Mi3W SIM not recognised - peculiar case

Hi All. I have quite a strange case of my SIM card not being recognised by my Xiaomi Mi3W.
Here's what happed.

1) Purchased phone off friend with stock MIUI - all working
2) Inserted my SIM with mobile carrier A (still with stock MIUI) - all working
3) Flashed Cyanogenmod 12.1 Cancro on phone - all working
4) 3 days later, changed mobile carrier to carrier B - not working
Original SIM card from carrier A was in phone when my account with carrier A was erased.
Since my number was ported from carrier A to carrier B, the phone has had issues recognising SIM cards.
5) SIM card from carrier B not working, and neither are other SIM cards
6) I have checked with carrier B and my phone is definitely compatible with their network.
7) My SIM card is working on all other phones
8) The weird bit is that at the shop of carrier B, the shop assistant SIM worked, but a brand new SIM didn't.
9) I have tried reflashing Cyanogenmod. - not working
10) I have updated Cyanogenmod. - not working
11) SIM tray looks clear of dust/obstacles - still not working

Not to sure where to go to next. I guess I can try back to MIUI or stock android, but I'd love to hear what you think.

Elephone p8 mtk6592 not recognised by computer after flashing a rom

Hi there all,

I have tried to flash a rom but after that now the phone is not working any more; no power, no charging,, no display nothing except the red light and a usb detection sound but it keeps disconnecting from the computer and there is nothing in device manager any more... please help...

thanks in advance...