How to completou delete SMS online backup

[MataRatos]

I'm having a lot of trouble retreiving and deleting my online SMS... I have a 640 that I'm not currently using. But I have it on all day long to see if I can retrieve and delete 5 SMS I have online. I Know that they are there because I can see them in the WP Message Backup app. But they don't appear on my phone... I did several hard resets, my phone is currently on fall CU, I have it on for months, rebooted several Times, and nothing... Every time I reinstall the WP Message Backup app on my PC it retrieves the same SMS, so they exist on the servers, but I can't find a way to delete them.

 

[T Moore]

Were the messages you see created when the phone was on 8.1?
Probably why the phone on 10 will not retrieve them.

 

[HoosierDaddy]

Were the messages you see created when the phone was on 8.1?
Probably why the phone on 10 will not retrieve them.

FWIW, I still have all my SMS mesages on my L950XL, going all the way back to 2013 and my L521 and numerous Windows Phones in between.

 

[MataRatos]

The 8.1 SMS I deleted long ago. When I do a device rcovery to Windows 8.1, there are no SMS. and also on Windows 10 there are none. they appear only on that app, WP Message Backup.