For some reason, I suddenly can't place a bid on eBay...

I placed a few bids yesterday. Later I tried to bid on one or two more items and when I clicked on the "place bid" button, nothing happened.

I CAN increase bids on items that I've bid on...but can't place a new bid.

It first happened on my Mac, using Safari. Today I tried again, with the same results...so I tried using Chrome, same results. So I tried using our desktop, which uses Windows 8...tried with Internet Explorer, and Chrome...nothing will work.

There are no messages in my inbox from eBay...and I can't figure out how to contact them, since my issue isn't one that they've got listed (as far as I can find).

Help...?