Thank you for your response. I don’t know if you received my last email.
I checked the cache. it’s okay.
I deleted the plugin and re-installed it with the same results.
I successfully installed it on 2 other network of multi-sites.
It seems it is a problem with the main Network.
So if you would be nice enough to look into this, I would take any insights to solve this.
For now I will use a subdomain in the network accepting the plugin.
Thank you!