ASP.NET Core API 500 Internal Server Error when uploading file on IIS

I'm working on an API project that needs functionality to upload files. When I run the project on localhost and try to upload the file, it works fine, but when I publish the project and deploy it on IIS, the upload doesn't work and produces a 500 Internal Server Error.

    [Authorize]
[Route("api/[controller]")]
[ApiController]
public class UserFilesController : ControllerBase
{
    private IConfiguration configuration;

    public UserFilesController(IConfiguration iConfig)
    {
        configuration = iConfig;
    }

    [HttpPost]
    public async Task<IActionResult> PostFormData([FromForm]IFormFile file)
    {
        var dict = new Dictionary<string, string>();
        HttpContext.User.Claims.ToList()
           .ForEach(item => dict.Add(item.Type, item.Value));

        string userid = dict.ElementAt(2).Value;

        FileConverter fileConverter = new FileConverter();

        if (file == null || file.Length == 0)
            return Content("file not selected");

        var path = Path.Combine(
                    Directory.GetCurrentDirectory(), "File",
                    file.FileName);

        string ext = Path.GetExtension(file.FileName);
        string newFileName = Guid.NewGuid().ToString();
        var filePath = Path.Combine(Directory.GetCurrentDirectory(), "File", newFileName+ext);

        using (var stream = new FileStream(filePath, FileMode.Create))
        {
            await file.CopyToAsync(stream);
        }

        fileConverter.ConvertToPdf(filePath, newFileName);

        var pdfPath = Path.Combine(
                    Directory.GetCurrentDirectory(), "File",
                    newFileName+".pdf");

        DateTime ExpiredOn = DateTime.Now.AddDays(1);
        DateTime CreatedOn = DateTime.Now;
        string fileUrl = "/File/" + newFileName + ext;
        string pdfUrl = "/File/" + newFileName + ".pdf";

        using (var connection = new NpgsqlConnection(configuration.GetValue<string>("dbServer:connectionData")))
        {
            connection.Open();
            try
            {
                string createdon = CreatedOn.ToString("yyyy-MM-dd HH:mm:ss").Replace(".", ":");
                string expiredon = ExpiredOn.ToString("yyyy-MM-dd HH:mm:ss").Replace(".", ":");
                var value = connection.Execute(
                    "INSERT INTO uf (ufid, name, oriformat, fileurl, pdfurl, createdon, expiredon, isdeleted, systemuserid) VALUES (uuid_generate_v4(), '" + file.FileName + "', '" + ext.Replace(".","") + "', '" + fileUrl + "', '" + pdfUrl + "', '" + createdon + "', '" + expiredon + "', false, '" +userid+ "');"
                    );
            }
            catch (Exception e)
            {
                return BadRequest(e.Message);
            }
        }

        TableUserFileBaru result = new TableUserFileBaru();

        using (var connection = new NpgsqlConnection(configuration.GetValue<string>("dbServer:connectionData")))
        {
            connection.Open();
            try
            {
                var value = connection.Query<TableUserFileBaru>(
                    "select * from uf where systemuserid = '"+userid+"' order by createdon desc;"
                    );
                result = value.First();
            }
            catch (Exception e)
            {
                return BadRequest(e.Message);
            }
        }

        string ori_format = result.oriformat.ToString().Replace(".", "");

        PostUserFileResp resp = new PostUserFileResp();
        resp.UFId = result.ufid.ToString();
        resp.Name = result.name;
        resp.OriFormat = ori_format;
        resp.FileURL = result.fileurl;
        resp.PdfURL = result.pdfurl;
        resp.CreatedOn = result.createdon;
        resp.ExpiredOn = result.expiredon;
        resp.SystemUserId = result.systemuserid;
        resp.IsDeleted = result.isdeleted;

        return Ok(resp);
    }
}

Update: After following ArunPratap's steps to display the error details, I got the following message.

An unhandled exception occurred while processing the request.UnauthorizedAccessException: Access to the path 'C:\inetpub\wwwroot\NetCore\File\7ebb3a76-f194-41f2-8a4b-a576308856aa.pdf' is denied. System.IO.FileStream.ValidateFileHandle(SafeFileHandle fileHandle)

Does anyone after me know how to fix this? thanks.