Depending on how many days pass from the time you miss the workout, you can start your program back up with the workout you missed and go from there.
If a lot of time has passed (over a week) doing something is better than continuing to do nothing! So, ideally you’ll pick a day from your plan you know you’ll be able to do and build back momentum from there. You can even combine exercises from a few different workouts just to get yourself jumpstarted and going again, then fall into the rhythm of the prescribed plan.