Have you tried the usual "fix" of clearing cache and cookies then rebooting your computer ?

You could also try a different browser (I use Firefox and Chrome with very few problems).

I would try what Padi suggested first. It might also be a temporary glitch though.

You could also explain the situation to the seller and ask him/her to cancel your bid. I think sellers can do that?

I have never retracted a bid, so I am not sure if there are other options, but I think if you can't because there is a glitch, letting the seller know ASAP is probably a good idea.

I don't know if there might be a maximum number of bid retractions allowed?

Hi, I am having the same issue and tried on multiple computers, I also put in the wrong bid amount and I cannot change it. 

Same here. It's been half a month and the bug is still not fixed. 😞

"Ebay live chat's told me to Win the auction, not pay,  then raise a ticket to get any marks removed from your profile  (no joke)."

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Can't believe this part. 

The eBay bid retraction system has been down for a couple of months at least. I’ve tried on my mobile on multiple browsers and on my pc and it doesn’t work at all. eBay I hope your reading this chat! Please fix your broken system!