If you experience an error "Cannot charge because amount is too high" while trying to charge a guest, please, make sure you have a correct set up for the exchange rates.
The system tries to prevent you from overcharging the guest as the amount seems to be too high.
You need to navigate to the Main menu > Settings > Property > Exchange rate, where you see what is the rate the system uses for the charge. If you have an incorrect rate or have it as 1 -> 1 it can be a reason for the error message.
More information on setting up the exchange rates you can find in the following article: