It’s difficult to debug from just that error message.
But it is a generic error that is only sent when the message fails and the error is not a WP error.
From your description, the error is specific to a single site, so something has changed on that site or on your hosting plan.
Using WP_DEBUG may give more info.
Thank you. Was thinking the same. I think its related to my hosting provider…but I can’t get them to budge.
Being mostly a novice at this—do you have any speculation and where to look? permissions issue, HTAccess, wp-config. any clue is appreciated.
Thanks for responding I realize we need more.
Will be trying to enable WP_DEBUG.
Thanks
Mike