@arxontas More info may help getting added responses....
What changed - it was working fine .. then ...
Updates? Installed new App/Hardware - Kernel etc.. ? ??
The last time it worked - do you have a backup (Systemback in LL3.x) reverting back may help alleviate..
Any config changes to the router? Specific changes to the network card - i.e. static or dns entries....
What type of card / driver - could start with the output of
inxi -n
What Kernel version
uname -r
Something else to try - if all else...
It being a desktop - could also try a pci NIC card to rule out hardware - perhaps the onboard is going bad???