[WPMU DEV Dashboard] WPMU plug-ins not updating

None of my WPMU plug-ins are updating on this site. I use the HUB to update all my sites, but these 5 plug-ins never update from the HUB. When I go to Admin, I manually update them but even though I get a positive confirmation that they've been updated, they aren't. Can you help? All my other sites work perfectly. thanks, Kim