I have the same exact issue.
I tried the manual detach using the two holes in the Clipboard and I managed to detach the Clipboard and then charge it.
Now, it is charged; however, this is not sufficient to restore the problem.
I connect the Keyboard again, the PC does not recognise the Keyboard, and the Red Light comes back on to be turned constantly.
Tried to clean the connectors, still didn't work.
Tried the BIOS, restart, still nothing solved.
Tried to recovery, and restore the PC, same, did not work.
I disconnected manually the Keyboard and connected it several times, and still doesn't work.
...
The USB in the keyboard does not charge another device...
Is the 8 days waiting the solution ? i.e. completely drain the second battery before connecting them and charge again... ?