My bike when new did not want to track. There was a definate bias to head left. After pondering the situation for a while I checked the alignment of the front and back wheels. I did this by turning the bike upside down, then shimming under the handlebars until the back wheel was perfectly plumb using a carpenters construction level. I then ran a string alongside both wheels and turned the handlebar until both wheels were aligned with the string. At that point the front wheel should also be perfectly plumb but it wasn't.
What I found was that the front wheel was tilted. One of the dropouts in the front wheel was inserted incorrectly by just a tiny bit. The geometry is such that if the front axle is off by even 1/2 mm, the rim is off by 4 to 5 times that and the wheel will not track properly. I ended up filing the dropout the axle sits in with a round file, just a bit at a time until the wheel was plumb and also perfectly aligned with the string. Now the bike tracks well although I believe tracking would improve a bit with a new fork having a bit more trail. This is not urgent so I've not bought a new fork. Good luck tracking down your problem.