RYOBI Jigsaw does not cut square

The Jigsaw may not be cutting straight because:

The blade might be excessively worn, bent, damaged, or not installed correctly.

The blade may of low quality which can also be the cause. An inferior quality blade can warp or deform when in use, even if the blade is square after use. A higher quality blade is often thicker and will stay sharper much longer.

As Jigsaws are a free moving tool, it is possible for the tool to drift from the cut due to human error; you may want to consider using a straight edge to assist.

Ensure the blade is matching the material thickness. For example, thicker material requires a thicker blade.