You need to file an extension if you have not. Are you able to file an electronic extension?
https://www.irs.gov/filing/free-file-do-your-federal-taxes-for-free
If you owe taxes, and you are able to pay, you should make the estimated payment to avoid interest penalty.
https://www.irs.gov/payments
Also see:
Penalty Relief Due to Reasonable Cause
https://www.irs.gov/businesses/small-businesses-self-employed/penalty-relief-due-to-reasonable-cause
