Keep your existing visa for verification purposes, enquire about what happened because you'll have to regardless what channel you enquire in that being formally.
You'll need to reapply only if your circumstances do were not impacted by covid, otherwise your free to enquire, but your family will have to invite you again and also follow on on covid requirements, so either way your destined to reapply.
Hi! My mom's case is a bit similar to you. She has a valid visa when the lockdown has started and wasn't able to return. Now that Australia is opening up to parents of PR/citizens, we applied for a new visitor visa 600 for her and supplied all the documents required. There is a question on the form asking if the applicant has a valid visa when lockdown started and if yes, provide the expired visa grant number so that's what we did. After submitting everything, the immigration waived the $145 visa fee but they would still definitely asses her application as normal.