Auction purchase - drt , sub registrar denying registration

Usually, the DRT will issue proceedings to the auction purchaser and makes a copy to the Sub Registrar.  If you will able to get the new Proceedings from the DRT with the latest date then only the Sub Registrar can registrar.  Otherwise the SR cannot register with the old proceedings.

Ignorance of law is not an excuse.

The property was to be registered and transferred in your name within stipulated time.

If you are enjoying the possession and got mutation, contact a local advocate to file a declaration suit claiming the property on Adverse possession also.   In fact, if there is no litigation, purchasers may also take that risk but they may bargain and withhold some consideration as a deposit for future litigation or for publishing such news in newspapers. Contact a local advocate for exploring the alternates to get a sort of deed registered within a family for further authentic transfer to outsiders.

There is provision of appeal before District Registrar  under Registration Act for refusal to register. You may file appeal before  him stating how non-registration  came to your notice now. Or else, your case will be barred by limitation.

Perhaps, approaching the High Court in a writ Petition could provide the solution.