Customized page error after upgrade from 7.1.6 to 8.1.3

Hello,

Our OneIM on UAT environment just got upgraded from 7.1.6 to 8.1.3 with database upgraded via configuration wizard.

Everything was fine except 3 customized web pages.

The app server as well as web portal has been uninstalled and then re-installed after upgrade has made.

An error message box showed up with message 'Unable to get property 'responseData' of undefined or null reference' every time while we opened the web page.

Additionally, there is an error message on the page:

===== BEGIN OF THE ERROR MESSAGE =====

An exception has occurred while executing the form method AutoCompleteData_F0_ctl00_ControlRef8_ControlRef15_ControlRef15_ControlRef8b_Main_Main_ColumnEditor2_Container2_AutoComplete1.

Resolution of the dependency failed, type = "QBM.CompositionApi.Data.ISearchHelper", name = "(none)".

Exception occurred while: Calling constructor VI.WebRuntime.Data.SearchHelper().

Exception is: AggregateException - One or more errors occurred.

-----------------------------------------------

At the time of the exception, the container was:

Resolving VI.WebRuntime.Data.SearchHelper,(none) (mapped from QBM.CompositionApi.Data.ISearchHelper, (none))

Calling constructor VI.WebRuntime.Data.SearchHelper()


Exception has been thrown by the target of an invocation.

The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel.

The remote certificate is invalid according to the validation procedure.

===== END OF THE ERROR MESSAGE =====

Could anyone help fix the error?

Thanks.