I have the same problem. with Q17 (126.96.36.199 - Win10. I talked with Quicken support today, they did not have an answer when I asked if this was a known bug. My symptoms are the following: If you go to Mobile and Alerts page, on the bottom Right where you select the "Budget To Show on Phone or Tablet" - no matter the budget I select here, the panel always shows "No budget selected".
The work around process I have to follow then, is to sync everything, do my work within the Desktop Application, and the last step is to go to the Mobile and Alerts Page and select the budget. I do this every time I sync my mobile devices, I have to go to this page because the Desktop Application never saves the budget that is selected. So anytime you sync to cloud, the desktop thinks there is no budget selected because it never saves the budget you select.
I have tried selecting other budgets, copying budgets. No budget ever saves.