What is causing my model’s shoes to detach from the leg?

Question

I am doing rigging here. I had made a pair of boots so I can use them on several models without going through all the trouble of making them again. On my first three models, I’ve deleted on the shin/foot/shoes on the original models, put on the boots, assigned them to the bones, adjust the bone weighting a little bit, then done. They work perfectly.

However, on my forth model, I tried putting on the boots like the other models. It won’t work. You see the boot is not attaching to the leg, I’ve checked the bone weighting but it is correct. The fourth model is from the same game as my previous models.

Fourth Model (original):

After I put the boots on and assigning it.

Bone weighting:

Answer 1

To have the boots painted red is not enough: boot vertices have some weight relatively to others not moving bones that force them to stay in place. In edit mode select one boot vertex that should move and check in the "N" panel all its weights assignements, to identify which weights to delete from which unwanted vertex group.

They should have weight on Thigh, Foot and Toe vertex groups only, and surely this is not the case.

Answer 2

I fixed it! I just found out the same boot was assigned to the shoulder bone for some reason. After I removed the weights it worked! Thanks for the advice!