You actually want to do a simple thing. Where did you print the alpha value? Is it inside the AnimBP? It’s important to print it in the AnimBP because you need to ensure that the variable’s value is correct. Was the Transform Bone node configured correctly? Does the door open when you change the values in the Transform Bone node while in the editor? Are you sure the Transform Bone node is correctly configured? Did you use “Add to Existing”? Did you set it to Component Space? Connect the alpha value directly to the node’s alphas and set the rotation Z to 90.
Check the things I wrote above, and if it still doesn’t work, send me a screenshot of the Transform node properties so that I can see them.