Everything that is on that card is gone.
Once you made the card "Internal" storage it was encoded to work with only that device. When that was done, certain things were put on the phone to make the card able to recognize it. When you reset the phone, you wiped the connection. There is no way to get it back.
You can use the card again, but you would have to format the card, which will erase everything on it. However, that won't really make a difference in your ability to get any of it, because it is not accessible by any device now (the data), so formatting at least will give you access to the SD card to use for new data.
Should you choose to format it and make it "Internal" again, or get a new SD card and do so with that, just make...