I couldn't use coins to buy a card

[Homer602]

It has now happened for the third time.
I couldn't use coins to buy a card.
When the mouse cursor was over the card to be purchased, a question mark appeared next to the mouse cursor. But the ticket could not be bought. Although the supply of coins would have been sufficient.
That's how I lost the game, but I also lost my reliability.
Has anyone else had this experience?
What can I do to get reliability back?
Thank you for your help

[nickiiie]

Were you playing competitive? In that mode when you have both gold coins and the correct color coins, you have to click the coins you want to use (gold or color). In casual mode the computer automatically uses the color coins

[riwu]

Same problem here. Yes this is Arena mode (competitive).