About D visa application

Hello,I got single permit last january but I have not applied for D visa yet.  Because the employer does not get work and asks to wait.  Is there any requirement to apply for visa within how many days.Work permit is valid till October last .Can anyone reply.

@Hiba Fathima P. S


You can find the single permit validity at the top of the email sent from  immigration to the employer granting  Annexe 46