Modeling a kitchen sink - Bevel issue UPDATE: Included the .blend file: 
Blender novice here. I'm trying to model a kitchen sink and i'm having an issue immediately with trying to bevel a certain edge. I've looked through various of the suggested questions/answers but it didn't really help me. This is the sink i'm trying to model:

I've created the basic mesh in blender as shown below:
Solid view:

Wireframe view:

I'm trying to bevel the edge as shown below but the beveling doesn't seem to happen along the expected edges:

By contrast, when i attempt it on one of the other edge, it seems to happen as expected:

I suspect it's not working because there are additional edges/vertices that i need to be taking into account or including at the bevel attempt? Could someone assist?
Many thanks!
I have opened your file and checked that you have 26 overlapping vertices. try going to mesh then clean up - merge by distance.