Having issues with merging bodies…help

I select all the body and click unite and it starts to work then goes back to nothing…so I literary cant merge the body and they all connected touching…still having issue need help plz

Hi! Please apply the tool to a smaller group of bodies to find the problematic parts. If you apply the Union to a group of objects, it is not easy to find out which body makes the tool fail.

In your screenshot, there seem to be some edges along the side and circular faces. The Boolean tools work reliably if there is a clear overlap between the bodies instead of tangent faces. Can you please check if there is an intersection between the bodies?