Question for problem with certificate pidgin

[Manuel]

Hello I need support to configure pidgin, we are using XMPP protocol to
connect to a openfire server.

When I tried to connect pidgin send the message  --> "Unable to validate
certificate"

"The certificate for jabber.policia.rionegro.gov.ar could not be
validated. The certificate chain presented is invalid"

I tried to copy the certificate from other PC that work (with old pidgin
version) on my computer but the message is the same.

I think with old version of pidgin work rigth.

We use Ubuntu mate 14 and pidgin 2.10.9

It is possible to install a old version of pidgin on my operating system.

Regards.
Juan Manuel.