If you made a mistake with the maximum bid by entering a wrong digit or decimal point in error, you can retract the bid and then place the correct bid.
If the seller has changed the item description after you placed a maximum bid, yes.
If you placed a maximum bid in order to see other biddersโ maximum - no. Thatโs against eBay policy.
If the auction has ended and youโve won the item, no.
See eBayโs Help page on bid retractions: https://www.ebay.com.au/help/buying/bidding/retracting-bid?id=4013