I note that when you open a B4A project in the IDE, the path to the assigned private sign key is not loaded by default (it seems to retain the path to the previously opened project).
Is this expected behaviour, am I configured incorrectly, or am I missing something?
The global sign key path should be saved when you close the IDE. Make sure that you don't have multiple instances of B4A running, change it, close the IDE and reopen.