I get this all the time during my dev. ALWAYS something (stupid) I did (added) to the page. Inspect page may (or may not) show the issue.
Often, I have to roll back to find what caused it - if I can't see it in code... but, as always... it is in your code - not in this dev environment - as has been proved to me many, many, many times.
Low bandwidth will leave your page hanging. I have a site when trying to be reached over a sat connection would just spin the ' circles '.
The load for the site is low, yet still cant understand why this is so....
We shall (eventually) get to the bottom of this issue.
AddModalSheet is like AddComponent. As long as you did not do a page.refresh, it does not exist on the browser side so running ShowModal() at that point is propably causing 'the hang'
So probably (untested) could work:
B4X:
Sub ConnectPage()
page.AddModalSheetTemplate(testsheet)
page.Refresh ' IMPORTANT
page.FinishedLoading
page.ShowModalSheet("mytest")
End Sub