(Urgent) Bridge edge loop error (When I combine two objects)_it looks like being pinched

When I combined two object( Ctrl+J) then I tried to connect edges with bridge edge loop,
Then it always came out like this(it looks like being pinched…it drove me nut every single time…
Please help this out

Thanks

No internal faces and you have equal vertices on both sides?

Yes as you can see, it has 4 vertices on both sides!

Try recalculating normals with everything selected (Shift+N)

I was able to reproduce the problem when one object had normals facing the wrong way.