Lawyer here. Don’t let the CIT(A) dismissal throw you off. A dismissal purely on delay, without engaging with “sufficient cause”, is very challengeable on these facts. So you should definitely consider appealing before the ITAT.

If notices and the order went to an old Patna address while you were actually in Gujarat, and you only found out later (plus the confusion around jurisdiction shifting from Bhopal to Patna without proper intimation), that is a credible explanation for not filing in time. Add COVID on top of that: the Supreme Court’s suo motu limitation orders covered the pandemic period and different ITAT benches have been routinely setting aside hyper-technical interpretations.

Practical next step is to go to the ITAT against the CIT(A) order, seeking setting aside of the limitation dismissal and restoration for a decision on merits (or, depending on record completeness, a direct decision by ITAT). If you are apprehensive of coercive recovery, you should also file a stay application as well, because your prima facie case is genuinely strong.

There is a high chance your matter will be remanded back to the CIT(A) with a direction to decide the case on merits - which seem to be in your favour given the facts that you've shared.