Hi Alexchu01, your question has been redirected to Customer Support. They will come back to you via email to assist you further. 

Thanks very much for the answer；mine is supposed to expire by October 2021, but I want to extend to Oct 2022, not sure Eurail office can help？

Some weeks ago I received mail from Interrail that my pass ( mobile, bought in March 2021 ) is extended with 6 months, so 11 by low plus 6 bonus. 

Don't you have the same mail? 

Sorry, postpone to 2022!