Keil Studio Cloud stuck Loading... target hardware

I have used ARM Keil MDK to converted a CMSIS project for a FRDM KL25Z board to a .cproj format and then cloned it from GitHub as a new project in Keil Studio Cloud: 1.5.50. At first it worked - the project compiled and a binary was downloaded. It offered the KL25Z as a choice for the target hardware and I selected this. However, since I tried to connect to the hardware (to run a debug session) the target hardware selection is stuck at "Loading ..." and it is no longer possible to build the project. Reloading everything or clone the project again has not helped.

Can any suggest a fix?