Network will be busy atm due to price movements? Where is the address you're depositing to? If its an exchange it'll likely continue to be accepted, if you're buying something you might want to send them a message and see if they can extend the window (if they can't it'll likely just come back to you anyway).

Can you share the txid and what accelerator you used? You may also want to enable rbf for the future in case this happens again (I think it's in preferences).