Apart from many other errors that appear in Avast antivirus software, the Avast UI Failed to load error is common. It is the reason for wrong windows service configurations. To fix this error without any help then you can follow these – 
* Restart the Avast software if it is in use

* Change the startup type of computer from normal to manual* Run the Avast repair program 

* Uninstall and reinstall Avast on the device

Don’t forget to remove the residual files of Avast when you uninstall the program otherwise, they can cause problems for the new installation.

For more Details visit: How to fix Avast UI failed to load?