This error, like the one shown below, is usually caused in these circumstances by a discrepancy in the ILR programme aims.
If you navigate to the ILR for this learner, you will likely see that the Episode Hours table has not been generated. Below is an example screenshot of what this table usually looks like:
To enrol the learner on to the programme successfully, you will need to generate the Episode Hours Table by amending the Learning Start date for this Learner. From the screenshot below, you can see that the aims have a Start date in the future, and an Actual End Date that is in the past, which is invalid:
Correcting these dates will generate the Table, which should allow you to enrol the Learner back on to the programme.