Fortnite V-Bucks synchrony is not working?

My girlfriend loaned me her PC for a few days. Today I have to give it back, but I have logged on the PC my account and 2,400 V-Bucks. Now the problem:

Mainly I play on the Nintendo Switch, where the V-BUCKS are not on it due to a synchronization error. The stupid thing is that the V-Bucks would be gone then.

How do I sync the V-Bucks to the Nintendo Switch?

Every time before buying V-Bucks, the game comes into play: Purchased V-Bucks are not available on other platforms. Conclusion: Your V-Bucks are only on the PC. This is not a sync error. Purchased V-Bucks are not cross-platform! You can't change that now. Your V-Bucks will not be available on the switch!