I had a problem with the Ambitions Firefighter profession where my Sim could maintain and upgrade the fire engine normally, but when an emergency occurred, selecting Respond to Emergency did not work. The Sim did not enter the fire engine and the emergency eventually disappeared.
The Fire Station was a placed community lot in Appaloosa Plains.
I edited the Fire Station and made two changes:
1. I moved the special fire-engine parking space farther forward/outward, closer to the road.
2. I added additional double doors around the fire-engine/station area to improve routing.
I then returned to Live Mode. At the next Small House Fire, Respond to Emergency worked: the Sim entered the fire engine, the engine drove out of the station and to the emergency, and the fire was successfully completed with a Grade A.
I don't know whether moving the parking space, adding the doors, or the combination of both fixed it, but after these changes the Firefighter profession began working.
One useful diagnostic: when I temporarily rotated the fire-engine parking space 180 degrees, my Sim could no longer even reach the engine to Maintain it. This suggests that the special fire-engine parking space has routing/orientation requirements and isn't merely a decorative parking marker.