I am unable to buy royal crystal. I have also chatted with Steam and they confirm it is not my steam account that costs the problem. Please kindly assist and help. Thank you very much!
Note: Steam overlay doesn’t work in my case (i.e. when clicking shift+tab).
I tried all the troubleshooting and nothing worked until I removed razer cortex. Try uninstalling razer cortex from the apps section of your computer. This fixed it for me.
Hello @unberkable and welcome to the Lost Ark forums!
Being unable to get your 
Royal Crystals is frustrating, especially if you’re trying to get something just as shiny! You mentioned that your steam overlay doesn’t work. Is there any particular reason why? To make purchases through Steam, you would need to have this enabled and working for the purchase window to appear.
To be sure, please go here, scroll down to Enabling the Steam Overlay and follow the instructions to ensure that you have the Steam overlay enabled and try to make your purchase again after fully closing Steam and relaunching Lost Ark.
Please make sure to respond as to whether or not that helped, so further troubleshooting steps can be provided if needed by me or someone else!