There could be many things gone wrong. It would be great if you post some screenshots where we can see the Bevel settings or even better a screen grab video to see where the mistake could be.
But usual suspects are, you have double vertices, so select all and M to merge by distance. Maybe your normals are flipped, so Shift + M to recalculate normals. You haven’t applied the object scale, so control + A to apply the scale.
.
