Industrial Disuptes Act Sec 33 (1) & Abandonment of services

We have an about 21 employees who are trying to form a union. These 21 people have been on strike since the last 5 months. We got a letter from the government to allow them to report back to duty and start work, however we have lost all major orders and been harassed to the point where all the non-union members have left.
They were supposed to report to work on June 1. two people did not report, one person reported after 5 days and we accepted him, the other person after trying multiple times to contact him etc, did not report to duty. After two weeks, we terminated his services due to abandonment of services.
Now he got a letter from the union to take him back or else its considered illegal under Industrial Disputes Act 33 1 b.
How can he choose when to report back to duty, because of him one machine sat idle for 2 weeks costing us a daily loss of 14,000 INR equating to 1,68,000 INR.
Can anyone please help?

Dear Shah,
May I presume that your query relates to the work-stoppage of your unit situated in India?
Forming an employees' union is a fundamental right in India. I think that the problem would have escalated to the level of strike by all the 21 employees in the establishment because of the indirect protest shown and the actions to scuttle the efforts against the union formation by the management. Agitation by employees en masse is a symptom of constant discontentment and formation of a trade union is a natural sequence and consequence as well.
You haven't mentioned under what circumstances the Government issued the letter to allow the striking employees resume work. Is it out of conciliatory talks conducted by any Labor Officer/ALC/DLC of the State Labor Dept or any Revenue Dept Official like Tahsildhar/Sub-Collector/ Dt Collector?
If it is an interim advice given by the Conciliation Officer appointed under the Industrial Disputes Act,1947 while the main issues are still pending conciliation before him, the employer can not punish any employee for any misconduct connected with the pending dispute by way of dismissal without the prior permission of the Conciliation Officer as per sec. 33(1)(b) or in respect of any misconduct not connected with the dispute, the employer has to seek the C.O's approval as per sec.33(2)(b) of the Act respectively.
That apart, the employer can not straight away dismiss an employee for the misconduct of abandonment of services without observing the due process of law like framing charges, conducting a domestic enquiry and the like. If he does so, the order of dismissal would be set aside in Judicial Review later as illegal resulting in reinstatement with back wages and continuity of service.
Therefore, tread cautiously and make amends accordingly in the interest of amicable industrial relations in the long run.