The manual says:
12. Manual start
The watch can be manually started after an unsuccessful restart. To do this, press the T4 (=upper left) button to cancel the automatic reception process.
Then press the T4 button again for more than 3 seconds to enter manual start mode.
I haven't tried this yet, just a guess: did you reset the watch before attempting this? It can't recall at the moment how to do this, but it's somewhere in this froum...