SSL - The signing CA is unknown

Hello.I bought an SSL certificate for my VPS (domain). Then I pasted the certificate into openfire. When I try to connect to openfire (conversation, gajim) it says:
the server certificate is not signed by a known certification authority.
I have also included my intermediate certificate in openfire.
When I try to transfer files between these clients, I get the error:
TLS verification failed. The signing CA is unknown.
What may be the problem?
Thanks for your help.

Does the Openfire admin console report the certificate as signed by a known CA?

Identity store:
Openfire certificate accepted.
In openfire - where can I check if the CA is known or unknown?

In Gajim - when I disable “https verification” in chat settings, I send and receive files without errors.