XBee Pro S2B with Arduino Wireless PROTO Shield PWR LED Blink and Unable to communicate with modem

I have 2 pro s2b part number is 30010242-02 rev a. One of them work well. The other one connect with Arduino wireless shield, the PWR LED always blink. Turn red for 1second then turn off for few seconds then turn red again and then off. when I use XCTU version to test the modem. It shows unable to communicate with modem. It was working well when I first use it. I uploaded an API firmware and then it comes with this problem.

Can you guys help me?

Thank you.

Which version of XCTU are you working with?

What specific version of firmware did you load on the module?

Have you tried selecting the Flow control function to Hardware and connecting CTS?