On the auction listing itself there should be an estimated date of delivery based on seller's dispatch time and the service seller offered (or that you chose to pay for). So I say 3 days dispatch time after payment, and I send by 2nd class typically so that's estimated 3-6 business days to arrive, or up to 8 days if you allow for weekend.
If seller said 1 day dispatch & sent first class or 24 hour service then you are right to expect item by now. Gotta check what you paid for.
I think you should wait for a reply from their email, I normally allow 48 hours for a reply, then of course it is the weekend too. I normally email a seller a week after payment if there has been no item or contact - some sellers don't mark the item as dispatched.
If you paid on Tues then 3 working days if Friday - so you would expect item posted then, and if 2nd class it would probably arrive Tues or Weds this week?
I think that's the difference between business & private sellers. Business sellers yes I'd expect them to find a way to check & respond to emails daily. Private sellers I expect to have a life. Ebay Corp. treats the 2 categories rather differently as a result of their expected levels of service.
Bargains are usually with the private sellers, but trade off is you get lower levels of customer service.
if you paid tuesday evening three working days for dispatch is friday, 2nd class delivers 90% within 3 working days ie wednesday, you can not open a not received dispute to the day after the last expected delivery date, if you go to purchase history ebay will have expected delivery based on sellers info of 3 day dispatch and it will say delivery between 17th-19th october economy delivery then earliest you can start ebay claim is 20th
if private seller you are expected to allow 48 hours for reply for business seller wouuld expect reply within 24 hours excluding weekends and holidays even with business seller an email on friday evening may not get reply till monday morning ( business sellers have a life too) but ebay does expect better service from business sellers they are expected to dispatch within 48 hours
I make it plain on listing that any item paid for after 8am on friday will not be posted till monday