Hey @shikha d, I've found out what's causing this issue for you, and it's nothing to do with your SSL certificate (that was a bit of a red herring, my apologies!)
The cause of this issue is articles created before we launched Articles Pro (in July 2019) and after we launched Articles Pro.
As part of the Articles Pro launch, and to prepare for multilingual Help Centers, we changed the format of Articles URL.
Any articles created before this launch are automatically redirected to the new URL format. The articles linked with your zeroda-help Help Center were created before this launch, which is why they're redirecting without issue.
However, any Articles created after the launch will only have the new URL applied to them - it's not possible to simply copy the old URL format and add a new domain (as it would appear you have done with your iifl-help and upstox-help Help Centers).
You will need to re-edit the links to the newly created articles (after July 2019) to link using the new format - it's not possible to use the old format, and there's no other workaround available.