My metal mesh band would not latch. The same problem as many other users experience. I took narrow pliers and I very slightly bent the vertical edge of the clasp of the mesh band outwards. This is the edge where the plastic latch of the watch falls into when latching. The required bending of this edge is extremely small. So do not overdo it! The bending is almost indistinguishable for the naked eye. One minute job and it works perfectly now! I think the same method could be used for the plastic bands, maybe you can first warm the edge up with the hair dryer to make plastic more flexible. But I have not tried it. The other solution for the plastic bands could be to file off a bit of the latching edge on the inner side. Success!
Moderator Edit: Clarified subject
