[Michael Romanos]

You will almost certainly be disappointed if your Corgi doesn't have erect ears - because that is a big part of a Corgi being a Corgi - the movement of the ears and being erect when excited, interested or alert to something.
At eight weeks, ears down. Ok. At 12 weeks, should be about up by now. At 16 weeks, oops, it must be time to tape. I often put soft or undeveloped ear controlling muscles down to a lack of sufficient calcuim. So that aspect needs to be explored. There is a min requirement for dogs of calcuim right from birth - and there is a max as well.