The route template separator character '/' cannot appear consecutively. It must be separated by either a parameter or a literal value. (Parameter 'routeTemplate') code example
Example: 'The route template separator character '/' cannot appear consecutively. It must be separated by either a parameter or a literal value. Parameter name: routeTemplate'
In my case, I had an extra '/' on my Route query string.
LIKE:
[Route("get/liked//{id}")]
[HttpGet("[action]")]
public async dynamic GetLikedPost(int id)
INSTEAD OF:
[Route("get/liked/{id}")]
[HttpGet("[action]")]
public async dynamic GetLikedPost(int id)