To know about cannot open avast user interface problem , you can follow these steps below:
1. On your keyboard, press the Win key.
2. Type the name of your Avast product. For example, Avast Free Antivirus.
3. Select your Avast product from the search results.
Hopefully, the above steps will help you to fix the issue if not you can also follow our blog on avast internet security won't open.