I have a announcement list where I give all users read permission. Everything was working fine and now everyone are facing issue in opening announcement item. It says 'This site has not been shared with you'. This issue is resolved if I gave them contribute privilege which they should not have. And I have exactly same issue with another list. Can any one explain what is happening.
Try to go to site settings->Site collection features->check if “Limited-access user permission lockdown mode” is activated, if so, deactivate and check if the issue exists.
If the issue exists, whether the Read permission is default permission level, check if the read permission level has Open permission.
According to the message
This site has not been shared with you you might have granted the needed permission on list or item level; in this case you should grant access to the start page/site collection.