Getting "Cannot find app" when opening UX App Config in UI Builder

[thomaskennedy]

I'm trying to build an interface in UI Builder. (We don't have the guided app creator.) All my tables and so on are set up, but when I open my UX App Configuration ("RFDevices") and click on Open in UI Builder I get 

Cannot find app fef0b6aa87b20d50d420f29acebb35a2
Choose an app here <link>

The window title is Application Not Found. The link goes to /sys_ux_app_config_list.do, which shows a list including the UX App Configuration I just had open.

I have wached every Youtube video on UI Builder, and completed the course on the learning site, and have no idea what the problem is.

[IndianaJones]

I had the exact same issue after upgrading from Rome to San Diego. Using cache.do resolved my issue

[sebastian_g_snc]

Thanks for the tip! cache.do fixed it.
Instance is on San Diego Patch 1 Hotfix 1

[Andy Smith2]

Thanks Brad - had a minor panic here after an upgrade of our Dev instance to San Diego - resolved with a cache.do !

Many thanks

Andy