Why will the chain on the chainsaw not cut properly?
Several things could contribute to this.
Chain orientation needs to be correct, a chain will only cut in one direction, alternatively the chain is dull and needs sharpening/replacing.
If you start to notice charring of the cutting material or sawdust rather than wood chips, this is a good sign that the chain could be dull.
If the chain cuts at an angle you may have a damaged chain bar or have cutters which are sharper on one side than the other. Consider replacing the chain.