Thanks for all your help. Your responses were quite helpful.
The issue has been resolved and the cause of it was the length of the session key.
Please, I would solicit for better response reasons in error messages. And I know, of course, not just me, but other developers as well.
I also found out that the length of the topic could also be an issue. So please, better error messages would really help.
If the error message was more narrow and pin-pointed, it would have saved us the week spent troubleshooting and seeking help in the forum.
Once again, thanks and best regards
@godwin.owonam