I'm trying to accept a safetrade and i get this...

You cannot access this account.
This item is not yours.
You cannot access this account.
This item is not yours.
You cannot access this account.
This item is not yours.
You cannot access this account.
This item is not yours.
You cannot access this account.
This item is not yours.
You cannot access this account.
This item is not yours.
You cannot access this account.
This item is not yours.
You cannot access this account.
This item is not yours.
You cannot access this account.
This item is not yours.
You cannot access this account.
This item is not yours.
You cannot access this account.
This item is not yours.
You cannot access this account.
This item is not yours.
You cannot access this account.
This item is not yours.
You cannot access this account.
This item is not yours.
You cannot access this account.
This item is not yours.
You cannot access this account.
This item is not yours.
You cannot access this account.
This item is not yours.
You cannot access this account.
This item is not yours.
You cannot access this account.
This item is not yours.
Cannot send items

Try resetting the safetrade.
Or just send whatever you want to send through Transfer Items/Toricredits instead. Then have the other person send their half.