foxitpro has to be registered (commonly referred to as 'associate with') with Windows as the STSTEMS PDF viewer.
All Calibre does is 'ask the system' what to use for PDF. It sounds like you uninstalled Adobe, so the system has no registered PDF viewer.
Easy test: Find a PDF file in explorer: Double-click it. If a viewer opens up with the file displayed-
Windows has that program registered to open PDF's and then I don't know why Calibre is having problems
If it fails. you need to cure the associate problem. Right-click any PDF: Properties: Set the Open With and tick the 'always use' box