Avast doesn't let Skytest program

My Avast antivirus 20.8.2432 doesn’t allow to open Skytest program. No any alert or notification of a threat. And I am sure Skytest is safe and virus free.
When I remove Avast, Skytest works with no problem.
This is link of program. https://www.skytest.com/DLR-Test-Preparation.htm

Any ideas or solution ?
Thank you.

https://support.avast.com/en-ww/article/298/ (Blocked & Allowed apps)

That menu is not available for me. Because no shield installed.

  • Which Avast…? (Free/Premium)
  • OS…? (32/64 Bit…? - which SP/Build…?)
  • Other security related software installed…?
  • Which AV(s) did you use before Avast…?
  • Which Avast…? (Free/Premium)
    Free 20.8.2432 (20.8.5684.604)
  • OS…? (32/64 Bit…? - which SP/Build…?)
    64 bit - Windows 10 Home 2004
  • Other security related software installed…?
    None
  • Which AV(s) did you use before Avast…?
    None

You can report a suspected FP (File/Website) here: https://www.avast.com/false-positive-file-form.php

Thank you. I submitted the exe file. When will I receive a solution ?

You’re welcome.