Identity Db Context Get Null In Web API

I have created API in .net 7.0, I have EF core with IdentityDbContext. Problem is when I am going to find user by user manager as below get null exception.

System.Data.SqlTypes.SqlNullValueException: Data is Null. This method or property cannot be called on Null values.
at Microsoft.Data.SqlClient.SqlDataReader.GetFieldValueFromSqlBufferInternal\[T\](SqlBuffer data, \_SqlMetaData metaData, Boolean isAsync)
at Microsoft.Data.SqlClient.SqlDataReader.GetFieldValueInternal\[T\](Int32 i, Boolean isAsync)
at Microsoft.Data.SqlClient.SqlDataReader.GetFieldValue\[T\](Int32 i)

I have tried to get user in login action.

[HttpPost]
[Route("login")]
[AllowAnonymous]
public async Task<IActionResult> Login([FromBody] LoginModel model)
{

    var user = await userManager.FindByNameAsync(model.UserName);

    if (user != null && await userManager.CheckPasswordAsync(user, model.Password))
    {
        var userRoles = await userManager.GetRolesAsync(user);

        var authClaims = new List<Claim>
        {
           new Claim(ClaimTypes.Name, user.UserName),
           new Claim(JwtRegisteredClaimNames.Jti, Guid.NewGuid().ToString()),
        };

        foreach (var userRole in userRoles)
        {
            authClaims.Add(new Claim(ClaimTypes.Role, userRole));
        }
        var authSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(_configuration["JWT:SecretKey"]));
        var token = new JwtSecurityToken(
        issuer: _configuration["JWT:ValidIssuer"],
        audience: _configuration["JWT:ValidAudience"],
        expires: DateTime.Now.AddHours(3),
        claims: authClaims,
        signingCredentials: new SigningCredentials(authSigningKey, SecurityAlgorithms.HmacSha256)
        );
        return Ok(new
        {
            token = new JwtSecurityTokenHandler().WriteToken(token),
            expiration = token.ValidTo
        });
    }
    return Unauthorized();
}