I had to use the "tape bridge" on Dudley. I only left it on for a day and a half though because he was completely miserable...I had settled on the fact that he was just going to have floppy ears, but when I took the tape off, both ears remained up! They have been up ever since. You might want to also look into some nutritional concerns. I don't know much about these things, but I'm sure one of the more knowledgeable corgi-owners might have some advice there. Then, there are some corgis who never get their ears up, but that doesn't make them any less great
Hopefully your patience will pay off! Good luck!