Cannot purchase gold with royal crystals in game

Hi all,
So I’m trying to purchase gold with my Royal Crystals and I keep receiving this error message.
I’m sure that my Steam account is trusted and verified ; I made a 5€ purchase on Steam more than 30 days ago.
And whenever I try to contact Steam support page, it says that Steam couldn’t assist me on other games (other than Valve/Steam games) and it redirects me to Amazon games webpage…
Plus, I have access to all Steam features (adding friends, community market and so on…) so I assume that my Steam account is trusted and verified.
The issue persists since yesterday night

Would be glad if someone can help me.
Thanks in advance!