itms-services throwing an error certificate for this server is invalid

Hello,

We have an enterprise app which we install it from our company's intranet site.

It used to work fine.

However recently we updated the certificate on the intranet site and the app cannot be downloaded anymore.

Whenever we click the link to download the .plist file it gives the error which we extracted from console.

Apr 9 16:13:40 D-iPad-3 itunesstored[86] <Warning>: Could not load download manifest with underlying error: Error Domain=NSURLErrorDomain Code=-1202 "Cannot connect to the Store" UserInfo=0x {NSLocalizedDescription=Cannot connect to the Store, NSLocalizedRecoverySuggestion=Would you like to connect to the server anyway?, NSLocalizedFailureReason=A secure connection could not be established. Please check your Date & Time settings., NSErrorFailingURLStringKey=https://portal.test.com/pappstore/Referralpor.plist, NSUnderlyingError=0x14db97e0 "The certificate for this server is invalid. You might be connecting to a server that is pretending to be “portal.test.com” which could put your confidential information at risk.", NSURLErrorFailingURLPeerTrustErrorKey=<SecTrustRef: 0x14ecb9a0>, NSErrorFailingURLKey=https://portal.test.com/pappstore/Referralpor.plist}

When we access the plist file from safari it works fine and opens up.

Can some please advise why this error is occurring?

Thanks.