Email queue "no data" after hitting Schedule Emails

After preparing a new campaign and click on “Schedule Emails” I go to Admin > Email Queue and I see “No Data” (no error messages). Emails are not sent anyway. I notice that if i click Send Emails on the Email Queue page (even if it reports No Data) the emails are sent and show up in the campaign report. I only tried with 3 contact in the target list. I really need this to work because I use Email Queue to send emails.

I just upgraded (with all the problems discussed in this forum) to 7.5 but it was acting the same on 7.3

No errors in the sugarcrm.log
Pleas advice,
Thank you Mauro

Just updated to 7.51 and the problem didn’t solve.