My parents filed the B2 visa extension in March 2020 as airport in Nepal was closed due to the Pandemic. When they filed the i-94 was still valid. They received the case number after filing the extension. They return back to Nepal in September 2020 as soon as flights resumed. 6 months after returning back to Nepal around March 2021, USCIS sent update to appear for Biometrics. As they already returned back to Nepal they were not able to appear in Biometrics. USCIS denied my parents B2 visa extension as they didn't attend biometrics and their I-539 petition got denied.
Now my question is- what will happen in this situation if they want to come back to US ? Is their Visa still valid (its valid till 2024, not sure if it will be void because the petition got denied)? what kind of documents they need to carry in port of entry ? Any one experiencing similar situation ? any input will be appreciated..