Why is PayU causing checkout errors in my Colombian online store?

Hello Shopify team.
I’ve built Shopify store in Colombia and integrated PayU as payment provider.
But now it has issues in checkout step with error message-“An error occurred while processing your payment. Please try again or use a different payment method.”

What is the reason of this issue and how to fix it.
I look forward to hearing from you soon.
Best, Rosario