Hi @vilas_shetty
Thank you for your updated information.
Yes, you can bring up one more flex UART using same FLEXIO instance.
I have a few suggestions for you:
1:You need config PIN and clock setting, maybe you can use MCUXPresso IDE PIN config tool.

2: I suggest modify code for FlexIO UART2, next code is just demo code

please try it.
Wish it helps you.
If you still have question about it, please kindly let me know.
Best Regards
mayliu