When you use timeseries() on a table object, then timeseries() does not look inside the table at the variables. It creates times 0:(rows-1) (seconds) where rows is the number of rows in the table. And the data associated with the time is the entire table row.
But table rows are not numeric, they are table() objects. And table() objects cannot be plotted.
If you have a table object that has a time field, you should consider creating a timetable(). There is no plot() for timetable objects, but you can access the Time property and whatever variable is appropriate.
Caution: If your times are categorical, then you have to be careful in how you construct the categorical in order to impose a sorting order and associated position values. Probably easier to datetime() with a 'convertfrom' to convert the categorical text into datetimes.