Sorry for the delay in getting back to you.
I eventually could not avoid upgrading my server to Centos 7.x with native PHP 7 loaded upon it; with Plesk Obsidian.
The whole thing was a complete and absolute nightmare, and I am only just getting things to normal.
I wish to report, now, that it looks as if the updates you made to PowerMessenger are working fine. I have only tried a couple of things for the last 5 minutes now that I have access again, and the few things I have tried to do with it are working OK
Thank you very much and I again apologise for the delay in getting back to you.
With every good wish,