GQueues add-on for Gmail "Spam and suspicious messages can't be used..." appearing on high percentage of emails in inbox

[Andrew]

Today I've started getting the message 

"Spam and suspicious messages can't be used for recommended content or actions. Try searching for messages in your inbox." 

on a high percentage of my legitimate mail in my normal inbox, when I try to use the GQueues add-on for gmail to create new tasks. 

Is anyone else getting this problem? Is it just me? 

Or maybe it's just suspicious for anyone to be sending emails during a lockdown?

If I forward the email to myself it is then OK, but that's messy. Not sure if this is a Google problem or a GQueues problem.

[Andrew]

Further investigation showed that it's where messages aren't authenticated - as indicated by the red ? to the left of the sender's address. A google search showed that users of Gmail add-ins for other apps (Evernote, Trello) are getting exactly the same message - so it must be a newish Gmail thing.

Thanks Google. :-/