"On hold" means you accepted the trade and Steam has put it under trade protection. The shop has already been told about your payment.
What trade protection is
Steam keeps traded items protected for up to 7 days. During that time the sender can reverse the trade from their Steam trade history. It exists to protect people whose accounts were stolen.
What it means for you
- Your payment is recorded and the shop knows about it.
- Each shop decides when it credits your order: some do it at once, others after protection ends. Ask the shop if your order is not there yet.
- The checkout and the find a payment page show when protection ends.
When protection ends
The payment becomes final and the shop has it for good. Nothing more is needed from you.
Items returned by Steam
If the trade is reversed during protection, Steam returns the items to the sender's inventory and the payment shows as reversed. The shop is told, and it may take back whatever it credited for that payment. Reversing a trade can also put your Steam account on a trading cooldown.
The trade was declined or expired
If the offer was declined, cancelled or never accepted, nothing was taken from your inventory. Start a new payment at the shop.
Check where your payment stands any time, see Check a payment and who to contact.