I believe the main fuse for the tranny on your 2000 is number 11. Probably says something like "cluster"
Check to make sure that the electrical connectors are tight.
Did you use the right filter? There are two different ones available. One is for shallow pans and and the other is for deep pans. You have to use the right one. If your pan is flat, you have a shallow pan. If it is stepped, you have a deep pan. Most Blazers came with a shallow pan.