unresolved variable in service callout

[krishnendusen72]

While running a GET call from postman I am getting one error in service callout unresolved variable.

Why I am getting this error?

I have attached the postman output please let me know if anything is needed.

[umannggoel]

@Krishnendu sen

Have you assigned any value to variable {upn_cached}.Which you have define in http target url.