*** temporarily SOLVED for my web ***
My PHP log content this:
[09-Aug-2017 08:34:23 UTC] PHP Warning: set_time_limit() has been disabled for security reasons in xxxxx/web/wp-content/plugins/mailpoet/lib/Subscribers/ImportExport/Export/Export.php on line 29
On Linux servers this does not work
Just comment the line on my website and it works OK, because it uses the time set by the server for this type of operations
It should have a conditioner depending on whether or not the server runs the set_time_limit command