Do you have an HR policy framed and approved by your top management for employee training and development programs? It should also include consequences one may face and disciplinary measures against those failing to attend despite providing them relevant information in writing.
1. First, you should seek a reason (in writing) for not attending the training program.
2. Seek inputs from respective department heads on what actions can be initiated, as it is the responsibility of the department heads to ensure that their team members attend the training program without fail. Verify the reasons submitted with department heads.
3. Kindly submit a list of nominees (absentees) to your top management, along with the valid reasons as received by you.
4. If your top management permits you to initiate disciplinary action, then you may issue a "memo," which can also be correlated with employee performance management systems.
The action initiated should educate your employees on a broader spectrum and should make them realize that such mistakes should not be repeated in the future, under any circumstances.
With profound regards,