Hello,
Sorry to hear you are having issues. But, from what I know, there is no auto-upgrade option available. I wonder, where did you purchased Fences 5 from? I believe, Stardock has stop selling Fences 5 since Fences 6 was released.

Perhaps you can request refund the Fences 5 and than purchase Fences 6. 

Thank you,
Basj,
Stardock Community Assistant.

Hello,
Sorry to hear you are having issues. Please raise support ticket using the link below, use the "Ask a Question" option. Include all information details. Remember to record down the ticket number for future reference if needed. Do not raise multiple ticket, that will make your ticket back to the end of the line. Send once and wait. Ticket will be answer by the order they send in.

https://stardock.atlassian.net/servicedesk/customer/portal/4/group/13 

Thanks
Basj,
Stardock Community Assistant