The trade was almost successful, but the sender of the payment did not click on “Payment sent”.
I received the amount, but cannot confirm “Payment received” its grayed out. How can I send him a note to make him activate his “Payment sent”?
Wait till the duration of the trade comes to an end. Then Arbitration will start and you can tell the Arbitrator that you have received the funds despite the other trader not having clicked “Payment Sent”.