If the Ciontek CS50C terminal cannot accept contactless payments due to card reading issues, you should:
Check if the customer’s card is contactless.
Slowly move the card close to the card reader of the terminal until you hear a sound; this indicates that the card details have been read correctly.
Ensure that the viva.com terminal app is updated.
Try wiping the terminals with a dry cloth.
If the problem persists, check the following:
Does it occur with both physical and digital cards?
Does the terminal not read the card at all (as if there is no card)?
Does the terminal read the card and then reject it?
Then, contact customer support for further assistance, mentioning the steps you have taken.