>>Have you maintained all the certificates correctly
I just saved the 3 .txt files (Certificate, Intermediate and Root) provided by my client as .crt.
Then I imported the same under "TrustedCAs" as "X.509 Certificate". The order that I maintained while importing the files was Certificate.crt, then Intermediate.crt and lastly Root.crt.
>>ensured that these are not expired ones ?
No they are not expired.