Without sounding rude or condescending, even if the amp is only 4 months old it is still second hand and prices for second hand items are rock bottom at the moment.
Given the poor prospect of a sale due to the current gigging and Covid climate you need to offer it at a bargain price just to get people interested.
I would look again at the price and offer it 50-70% of the new price.
Maybe not what you want to hear but it is realistic.
Good luck with the sale..... It really is a fantastic amp.