I am completely out of my mind that Avast Quarantine can remove a program I use every day! Do the exceptions expire? I am in the middle of using it and it stopped working for me to find its not even there any more! An exception was created at install. This has happened repeatedly so it appears avast itself is doing to me what it claims to protect me from. Thousands of people use this software but it is ‘not known’ low frequency called reputation.
As far as I’m aware exceptions don’t expire.
However, not knowing what your exception is or a screenshot of the Avast Alert with the See details option selected might help.
Did you except a specific file or a whole folder. You could try the latter.