All-in-one-security plugin blocks access

Hello,

as a websitemanager I’m using the MainWP-plugin to administrate multiple websites.
MainWP uses his plugin MainWP-child to connect with child websites and to have access on them.
Currently I have encountered the following error:

When I try to update a plugin with MainWP on a child website MainWP gives an error-message
which says, that the child-website could not reached and so the plugin could not be updated.

when I disable the All-in-one-security plugin the error mentioned above is gone.

Curiously, despite the error-message (child-website could not reached and so the plugin could not be updated)
the chosen plugin IS updated.

I want to go on using the All-in-one-security plugin, so I have tried this to locate the cause of the error:

• put the IP from the server which accesses the child-websites in the whitelist of AIOS on the child website
• uninstalled and reinstalled AIOS
• deleted the whole configuration of AIOS
• checked .htaccess-file for misconfiguration

Nothing has helped.

Could you please help me to solve this problem?

Sincerely jonathan789