Unexpected error message

A few days ago, the user send the mail to ask why error message" The webmaster has forbidden your access to this site" without no error code such as 403 comes out at his access time.  
The user's privilege is public and not loged in.  
Is there any case where securitycheck pro output the message to public user? If yes, what case?
Joomla 3.10.11
Securuty check pro 3.5..1
Site url:  www.enopo.jp/

Thanks in advance, T. Sejimo


 

Hi T.Sejimo,

The only way to know why that happened is checking the logs. Can you export and send me the file?

Regards,
Jose

I don't know exact time when the error message came out. I am afraid to send the log not including error information. So I stop to send you the log.
Instead, I ask you if you have seen such error message to the public user.
Regards, T. Sejimo

Hi T.Sejimo,

That message is shown every time a rule is applied; that's why I ask you to send the log.

Probably is caused by a false positive but we can't know why.

Regards,
Jose