In my opinion you should try something like that:

• First merge by distance as it seems like you have overlapping vertices
• You need to divide your sides like that in order to be able to fold them:

• Then lower down the chain of bones in order to put the rotation axis at the bottom, and create 3 bones that you make children of the bottom bone in order to control the top vertices and make the fold fold:

In my opinion you should try something like that:

• First merge by distance as it seems like you have overlapping vertices
• You need to divide your sides like that in order to be able to fold them:

• Then lower down the chain of bones in order to put the rotation axis at the bottom, and create 3 bones that you make children of the bottom bone in order to control the top vertices and make the fold fold:

• Frame 0:

• Frame 80:

In my opinion you should try something like that:

• You need to divide your sides like that in order to be able to fold them:

• Then lower down the chain of bones in order to put the rotation axis at the bottom, and create 3 bones that you make children of the bottom bone in order to control the top vertices and make the fold fold:

In my opinion you should try something like that:

• First merge by distance as it seems like you have overlapping vertices
• You need to divide your sides like that in order to be able to fold them:

• Then lower down the chain of bones in order to put the rotation axis at the bottom, and create 3 bones that you make children of the bottom bone in order to control the top vertices and make the fold fold: