Do you have
- Duchess Winifred
- Underworld Steed
- Reiser and Amara OR Asher
If you have all 3, you should have enough horse Shoes to craft the Ghost Alicorn.
If you have all 3, and you do not have enough Horse Shoes to craft the Ghost Alicorn, it's a bug and you should submit a ticket so S8 support can help you.
https://support.storm8.com/hc/en-us/requests/new
Good luck!