b1 b2 visas – How to check if you can still get admitted to US?

My parents were staying with a B1/B2 visa between last January and June. They had to leave on June 20th. They applied for an extension of stay before June 20th since flights were getting canceled due to COVID and they did not want to overstay. The application went back and forth between USCIS and my parents due to some mistakes in the application. In the meantime, they found a flight back to the home country around August 6th. So they had this application in hand that needs to be corrected and submitted back and at the same time a flight back to home. In the end, they left on August 6th and have not been able to resubmit the application.

The problem is they want to come back to the US however they do not know if their visa is still valid or if they overstayed or everything is okay since they already applied for an extension of stay before June 20th. In sum, how can they check they can still enter the US or their visa is still valid?

Unfortunately, they could not get an answer from the embassy in the home country.