Baiona is the correct spelling, but you need to be on the Camino Portugués de la Costa page to find it.
Then you have to check to see which albergues issue credentials.
Under Servicios y equipamiento Look for Expiden la credencial.
I assume that you mean Baiona, Spain which is on the coast. Another Baiona is inland in Portugal.
Gronze lists 1 albergue for Baiona, Spain, plus hostals, etc. The albergue does not list available Credencials. However you might email them for info.