My friend needs to tether from his phone to his pc because his internet will be installed in a week and he needs internet in the meanwhile so we've tried tethering and cheking options funny thing is though... my phone exact same model and seemingly same options aswell and mine can tether to hsi pc just fine but his phone cannot and it never has been able to do this we've tried this about ½ a year ago aswell wehre it also didnt work
If the phone came through a different carrier/service provider, they could have had that option restricted. Happens all the time. It could also be that the carrier/service provider, or the account type he has, has a restriction on this option.
Have they tried, instead connecting the phone to the computer via an actual cable, to connect it wirelessly. Using the phone as a hotspot?
If it is at all possible it would be done this way...
Go into "Settings" and in the "Wireless & networks" section tap "More".
Now tap "Tethering & portable hotspot".
For "Wireless Tethering" tap "Set up WiFi hotspot"
On this new screen you will see options for a "Network Name", "Security", "Password" and "Network Band". You can change them or keep them as is. It is really up to you.
Now you would just need to search for the hotspot by name using the second device.
NOTE: While a WiFi hotspot feature is built into Android, some service providers/carriers, especially in the United States, hide it. You would then need to see if you can locate an app that you can install to help with this.
Now if this won't work either, then I would bet it is the carrier/service provider that is restricting it. That one, no one can change but them.