Cannot Add Synoptic Panel by OKVIZ (Version 2.5.7.0)

Hello Roya-Daemi, 
Same error on a brand new PBIX is a useful clue honestly, rules out the report, so it's Desktop, the visual itself, or something local on your machine.

Looks like PBI's already got 2.5.7.0 registered somewhere and tries updating over it, and that's where things go wrong.

Some things worth checking to figure this out:

• What Desktop version are you on?
• Installing through AppSource, or did you import a .pbiviz file directly?
• Personal setup or a work/managed tenant? 

If it's managed, worth reaching out to your admin, ask if they've already pushed OKVIZ's visual org-wide. That's caused this exact kind of conflict before.

Also just try updating Desktop to whatever's current, restart it, then import again, quick thing to rule out.

Still broken after that?
I will recommend email OKVIZ directly and ask if 2.5.7.0 has any known issues, especially with whatever Desktop build you're running.