Working application but now start with blank page on start

Dear All

I had working with application that working normaly with wisej 2.5 (i had try upgrade to 2.5.38 it same error).

But today, when i want to make some minor correction i got blank start screen when start the application in visual studio 2019.

I had check default.html,json file and webconfig file, there nothing wrong.

I had check in chrome developer there error :

qx.js?v=2.5.38.0:174840 301048 Wisej: HTTP Error  0

GET http://localhost:63677/messagebox-warning 404 (Not Found)

Does anyone have experience solving this problem? (another application working perfectly)

Thanks

Nicky