You need to put a constant pulse into the rotation for the RInterp to continue to move. You will probably also need to replace the ‘time take to rotate’ with ‘get world delta seconds’. With that changed the current setup would increase the rotation based on what you have as the interp speed but only a fraction of it.
If you put a loop that goes through the rotation until the door reaches the open rotation and then cancel. That would make it work. Here is that setup.
You could also use timelines as per 's response but I find the interp way less hassle.