This is generally a time out connecting to a web resource.
I have found a lot of "fixes" on how to correct this issue but very few on how to isolate where the problem is. This is especially with Drupal where all you get is this general error:
Funny thing happened with Drupal 7.50, errors started appearing that I had no clue about. It started telling me about modules not being where they were supposed to be and about a utf-8 not being enabled.
One of the errors received was: