Why can't I join two Fire Offices together?

I was setting up a Fire Station in the city, I have added some stuff in there, and I press Fire Office. If I attempt to add a Fire Office adjacent to another one, so as to make a single and larger building, it won't go there. The UI gives me no warnings saying I can't place it there.

Would you help me please?

is the terrain level? As while there may be space for it to plop, it may not be able to level the terrain. Try removing one that you've had to space apart, then re-plop it right next to it

Is the road perfectly straight?

In the video you plop 3 down, but don't attempt to plop the 3rd right next to the 2nd. Could you plop the 2nd next to the 3rd? Could the specific position between the 1st and 2nd be the issue?