Dispute selling BEAM for BTC

Hello, I accepted an order to sell BEAM for BTC: I sent my beam but the buyer never connected to the wallet, so I had these beam stucked on ‘sending’. Now the payment figure as ‘failed’ because the buyer didn’t connect his beam wallet for 24 hours. Here are the 2 screenshoot (payment in process and after 24h payment failed).
What can I do since the arbitrator can’t really check the BEAM blockchain? I have already sent problem description and screenshoots to support.

Trade ID: ilfrns0-cd064404-ddde-4fa5-bf30-c0866d8e3c7f-093

2nd screenshoot of payment failed (buyer’s wallet offline)

I am not sure, not familiar with BEAM, but you should open a dispute either way and explain to the arbitrator your problem