Form 112 has to be sent when one is doing articleship. If you did not take due permission back then, then they will delay your membership.
If you did, then I wonder why they sent you that mail. Try re-sending the copy of the form, if you have any. Or, write a letter mentioned that you did..
For condonation of delay, you have just write an application, not sure if you are supposed to send form 112 now.
You can seek prompt response for your issue at e-sahayata: