I have updated the B4i IDE to the new beta (6.00 BETA #1) and I found it failed to compile my app.
Everything was working fine before I updated the IDE.
I then thought the Certificate / provision profile had an issue, so on the Apple Developer Console I deleted the files are started again. However still go the issue.
When I compile my app (in debug) it shows the error as attached.
Looks like the Mac did a update and updated to Xcode 10.3. It kept coming up saying it needed to do a reboot but I kept ignoring it as I was busy and didn't want to reboot the computer (like most people).
Did a reboot and now it seem to allow me to compile the app with the beta.