Hi David,
AB is little bit frustrating because I am getting this error since last night.
I have clear the caches and reinstall AB more than 5x today.
Navigation error: http://127.0.0.1:9999/
What could caused this?
{SOLVED} AB Unable to Display Correct Page
Compile, convert your modern HTML apps and games into Microsoft Windows executable programs without dependencies. 
Save time, resources and money creating apps for Android, iOS and more with the same base of code.
Apache Cordova's official plugins are supported out of the box and there are hundreds of plugins ready to use. 
Save money by purchasing our NeoPlugins bundles. Five, Ten and even the complete NeoPlugins collection at an incredible price!
Create multiplatform apps with DecSoft App Builder, including Android and iOS with the same base of code.
DecSoft App Builder integrates an Open AI assistant in order to assist you while developing your apps.
DecSoft HTML Compiler include a convenient Command Line Compiler, so you can compile your apps from the console.
Design for small screen devices but deploy also (without changes) in larger devices like tablets. 
Take a look at our YouTube channel and subscribe to be notified about new videos!
DecSoft App Builder include a convenient Command Line Compiler, so you can compile your apps from the console.
Create apps and expand their capabilities by using the world's popular programming language: Javascript.
Create modern HTML apps and games at another level making things impossible to do even by modern HTML apps and games.
DecSoft NeoPlugins put your VisualNeo projects into another level with +1,000 new actions for your apps.
DecSoft HTML Compiler is easy to use: set your project's options and compile your apps and games in a nutshell.
Take a look at some frequently asked questions about us and our products!
DecSoft NeoPlugins are available in both runtime and designtime flavours to keep your apps as small as possible. 
Hello edunt,
Please, if you have a different issue, open a new forum thread. Yo no need to worry about any cache at the first place. Also, reinstall the program without solve the problem may did not help. I really don't know what to say, since App Builder works fine here and I do not receive any other similar error report.
However, let me to shown how you can start with the program from scratch, so may the problem dissapear:
1º Uninstall App Builder from the Windows programs' manager
2º Be sure the installation directory has been deleted. Tipically it's located at: C:\Program Files\David Esperalta\AppBuilder
3º Manually delete these directories too:
C:\Users\[Put Your Windows User Name Here]\Documents\AppBuilder
C:\Users\[Put Your Windows User Name Here]\AppData\Roaming\AppBuilder
4º Download the latest release and install it:
https://www.decsoftutils.com/Download/AppBuilder
After follow the above steps your App Builder installation can be properly named "clean", so, hope the last problem you found dissapear. If not, tell me and may I can help you using Team Viewer, for example.
Hi,
After following your instruction I got different errer message which is {"reason":"Unknown command","result":"error"}.
Hello,
I am sorry, but I can't reproduce the problem here, so, it's difficult to help you. If you like, download Team Viewer and send an email at (info at davidesperalta DOT com) providing your ID and password, then I can connect to your computer. May look the problem by myself can help us.
Hi,
Problem solved by installed latest version 2016.44 (3rd January 2016).
Hello,
Well. That's very strange. But glad to know you got it edunt.
Everybody can read the DecSoft support forum for learning purposes, however only DecSoft customers can post new threads. Purchase one or more licenses of some DecSoft products in order to give this and other benefits.
DecSoft Feeds