Hi @Er Bo Guan ,
Which version of your SharePoint?
You could first check if the Anonymous is enabled in IIS Authentication.Then check if you enable Publishing feature at site collection level and site level.
And please check the features of your site collections via the following command:
get-spfeature -site http://sitecollectionURL
If ViewFormPagesLockDown is listed, it's enabled.
Please use the following command to disable it:
$lockdown = get-spfeature viewformpageslockdown disable-spfeature $lockdown -url http://sitecollectionURL
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