Getting error "Hmmm...can’t reach this page Try this Make sure you’ve got the right web address: https://localhost:5001"

Hello everyone!

My first post. Was thrown in the ring to write a razor app...

The app implements the PRG pattern whereby a search page is presented, the user enters a criteria, hits the search button and the result of the search is presented at the bottom of the same page. The items listed in the results table have a link that open a detail page, which has a "back" link to the first page. All that was working...I made some changes along the way and now when I run the app for the first time, it comes up. I enter the search criteria, hit the submit button and the page fails with 

"Hmmm...can’t reach this page

Try this Make sure you’ve got the right web address: https://localhost:5001..."

Below is a simplified version of the code in the page model.

[TempData]
 public string FileSearchCriteriaAuto { get; set; }
//...more code here
public void OnGet()
        {
            if (!String.IsNullOrEmpty(FileSearchCriteriaAuto))
            {
                FileSearchCriteria = JsonConvert.DeserializeObject<SearchCriteria>(FileSearchCriteriaAuto);

                HasSearch = FileSearchCriteria.FileName.Length > 0 || FileSearchCriteria.Criteria.Exists(c => c.Trim().Length  > 0);

                ContentSearchCriteria = new List<string>();
                ContentSearchCriteria.AddRange(FileSearchCriteria.Criteria);

                if (!(TempData == null))
                {
                    FileSearchCriteriaAuto = JsonConvert.SerializeObject(FileSearchCriteria);
                    TempData["FileSearchCriteriaManual"] = FileSearchCriteriaAuto;

                    if (TempData.ContainsKey("MatchedFilesJson"))
                    {
                        MatchedFiles = JsonConvert.DeserializeObject<List<FileProcessed>>(TempData["MatchedFilesJson"].ToString());
                        TempData.Keep();
                    }
                }
                FileName = FileSearchCriteria.FileName;
            }
            else
            {
                FileSearchCriteria = new SearchCriteria(string.Empty, 3);
            }

        }

        public async Task<IActionResult> OnPostAsync()
        {
            FileName = Request.Form["fname"].ToString().Trim();
            var elements = Request.Form.Where(e => e.Key.Contains("criteria")).ToList();
            ContentSearchCriteria = new List<string>();
            foreach (var ele in elements)
            {
                ContentSearchCriteria.Add(ele.Value.ToString().Trim());
            }
            FileSearchCriteria = new SearchCriteria(FileName, ContentSearchCriteria.ToList());

            string criteria = JsonConvert.SerializeObject(FileSearchCriteria);

            await LoadFilesAsync(FileName);

            MatchedFilesJson = JsonConvert.SerializeObject(MatchedFiles);
            TempData["MatchedFilesJson"] = MatchedFilesJson;

            return RedirectToPage("/Index");
        }

NB: I have tried passing a parameter to the OnGet method, from a property decorated with the

[BindProperty(SupportsGet = true)]

. Then the browser cannot render the page, as if the link is broken. 

Does anyone know why the page won't open? Thank you in advance!