My exclusions were wiped out (file paths) from previous avast version. Not sure when this happened or which avast update did this but not a happy camper about this. Plus trying to add a file path, and there is no input box for file paths, just the add button. Was going to post screen shot here but didnt see how to add this…
Help
Linda!
I would certainly advise backing up your settings regularly and certainly before a program update - avastUI > Settings > General - scroll down to the Back up settings.
As for posting a screenshot, under this text window:
‘Attachments and other options’
Click to expand.
here’s the screen shot…
Did it ever came to your mind to simply click the add button ? 
Yes, but you cannot add anything if there is no input field for the file path - Did that ever occur to you?
There is after clicking the button, if not there is something wrong with your installation.
It shouldn’t be necessary to click the Add button there should already be an empty input field there already. Enter your file path and hit your enter key and it should open another input field, without even having to hit the Add button.
There is certainly something wrong with the screenshot lindac2031 provided. For me the input field is present is available as soon as I open the global Exclusions section.
Repair Avast:
Control Panel> Program and Features (Add/remove program)>Select Avast> Select Repair. Reboot when completed
https://www.avast.com/faq.php?article=AVKB204
If Repair doesn’t fix the problem, try the following:
Clean Install of Avast:
https://goo.gl/4Ptzkf
My philosophy is if I have to reinstall a product do to its own bugginess then its time to try another product. Life is to short - DTM - Avast!
Au Revoir
Linda