Create meeting API gives 401 error on server

I use this endpoint -
Locally everything works fine.
But after deploy to k8s - I am getting getting 401 (Unauthorized).

Creating auth token like that:

     private string CreateAuthToken(string apiSecret, string issuer)
            var tokenHandler = new JwtSecurityTokenHandler();
            var now = DateTime.UtcNow;
            byte[] symmetricKey = Encoding.ASCII.GetBytes(apiSecret);

            var tokenDescriptor = new SecurityTokenDescriptor
                Issuer = issuer,
                Expires = now.AddSeconds(3000),
                SigningCredentials = new SigningCredentials(new SymmetricSecurityKey(symmetricKey), SecurityAlgorithms.HmacSha256),
            var token = tokenHandler.CreateToken(tokenDescriptor);
            var tokenString = tokenHandler.WriteToken(token);
            return tokenString;

What could be the root cause of that?
Thanks for your help in advance.

@shebalovdenis Was it working previously? If yes, it seems you were using JWT credentials. You need to migrate to the new server to server Oauth app type.

Here is the guide:

Thank you so much for your response.
Locally app and auth to zoom continues to work. I just have cheked.
It was my first deploy to k8s and auth failed with the first api call.
I am developing simple api app that creates links to zoom meetins.
Do you have any ideas what could be the cause of the issue that I faced after deploy to the server?