If there is no Place Bid button on the main page for that listing then either bidding has ended (or you are looking at a different listing that does not have bidding) or there is some issue between eBay and your device that the software isn't working to put up the button (in which case try a different browser/platform/device). A block or running into a limit does not cause the button to go away, you just get an error message when you go to submit the bid.
What are the item numbers? Can you post a screenshot of the listing page with no Place Bid button?
