1. If there's deviation from the sanctioned plan, occupancy certificate will not be given.  However if the deviation is little like upto 10%, the Corporation/Municipality may levy certain percentage of penalty and issue occupancy certificate.  

2.   Perhaps there's deviation from the sanctioned plan and hence the builder couldn't get oc for your building.

3.    You can go to consumer court even after 3 years.

4.     Consequences of not obtaining OC is, the flat/house/building is not suitable for human occupation, if the building crumbles/crashes resulting in injury or death to the occupants, the Government/ Corporation would not take the responsibility and no compensation would be awarded.

File complaint against builder before   consumer forum and seek roofers to direct builder to obtain OC within stipulated period 

2) also seek litigation costs and compensation for mental torture undergone by you 

You issue a legal notice to the builder demanding the OC and then file a complaint with the consumer forum for compensation for deficiency in service.

Dear client,  

In this situation, it may be advisable to file a complaint in the consumer court against the builder for not providing the occupancy certificate as promised. The consumer court can direct the builder to provide the occupancy certificate and can also award compensation for any losses or damages suffered by the buyer as a result of the delay.

Not having an occupancy certificate can have several consequences. It is a legal requirement to obtain an occupancy certificate before occupying a building, and failure to do so can result in penalties from the local municipal corporation. It can also affect the buyer's ability to sell or lease the property in the future. Additionally, if the property does not comply with the local building codes, it can pose a safety hazard to the occupants.

Lodge a written complaint with the State RERA authority against the builder seeking appropriate redress. Engage a competent lawyer and issue a notice to the builder demanding occupancy certificate to be produced immediately, and on default file a suit for specific performance in consultation with your lawyer. Agitate the issue before the Consumer Forum too.