DavidR:
I can confirm that clicking 'Remove' unblocked the app but, yes, I had to add it to the 'Allow' list so that it would not be blocked again.
Lastly, it does refer to the Ransomware Shield that I have enabled.
To answer your question, I was away from the computer when my office (word processing) software updated itself, which caused Avast to block it, which I only knew about the next morning.
Nonetheless, as a result of adding the office software to the 'Allow' list, it opened without any further Avast-related issues.