I have had this problem many times. For several days the sim goes to work when the carpool comes, however sometimes after many days, the sim just refuses to go to work, even clicking on his/her workplace and clicking on 'work' the task comes only to disappear as a completed task. 3 of my hard-working sims lost thier jobs coz of this only. and t ts not like i didnt send them

Try changing their work outfit. That usually fixed it for me.

Have you checked the workplace to see if the other co-workers are standing in front of the building with the no routing bubble over their heads?
If you have Master Controller installed check for 2 person jigs and flush them. From City Hall or a Computer>NRaas>Master Controller>Object Stats Something could be blocking the work entrance. Or try resetting the lot or town. If you have Overwatch and/or Error Trap installed it should be cleaning things up but sometimes it misses a beat
Also, when I've had that problem I've used MC to flush the RH jigs
You might want to save a copy of your game first before trying these things just in case the results aren't favorable for your game.

The moment i got a job, i have changed the outfit