All posts except most recent say "Comments are Closed"

For a few weeks now I keep finding all of my posts, except the most recent, stating “Comments are Closed”. If I do a quick edit I can click the box to allow comments. But who has time to go through and do that for 400 posts???

So how do I fix this? I’ve read past posting about this problem and either the solution was 6 years old, or the people with the issues were using other programs in conjunction with WordPress.

My blog is: https://www.futureflyingsaucers.com

THANKS!!