As daydreams said, we can't know what the problem is unless we have more details, such as the expected delivery date range.
It seems strange to me that you'd have the exact same problem with 2 different sellers and for the same item.
The expected delivery dates are very important. Once they pass, you can open an ebay claim for your money back, on the basis that you never received your items. You don't need to message the seller, you can do it independently. Do not close the claim till you get your money back, no matter what the seller says.
I see that you regularly give feedback to sellers. If you come across a seller who ignores your messages about a faulty product, you don't have to accept it as a loss, you always have that option of making an ebay claim for either item not received or significantly not as described.
The main thing though is to have a good look at an item, description and price before buying. Sometimes I have had disappointing experiences too (with cheap products). But I knew in advance that for the price, I couldn't expect too much. Especially if it is a cheap product that looks to be mass produced in China.
