Failed to add site. The sub-plugin was also installed on other websites, but it just can’t be linked. The following is the site reply
Hey @jianping
What error message do you get when you try adding the child site?
And can you please post the community system report from your MainWP Dashboard for review? The report is located in your Dashboard under Info → Server (your-mainwp-dashboard.com/wp-admin/admin.php?page=ServerInformation), on the top right of the page.
Be sure to use the button like the one below; this button hides all your private information:
Pressing the button auto-copies the report to your clipboard then just paste it in a reply here.
Also, can you please share the system report from your Child site? On the Child Site, navigate to your-child-site.com/wp-admin/options-general.php?page=mainwp_child_tab, SERVER INFORMATION tab, then click the Get system report button.