Users with access granted are unable to view site

Hello janphua 

have you created an SharePoint team site, communication site oder an team site groups connected?

When an groups connected team site, it's private or public?

The sites has different permission concepts:

https://docs.microsoft.com/en-us/microsoft-365/community/team-site-or-communication-site

When you have an SharePoint team site or communication site, add the group to your SharePoint site permissions:

https://docs.microsoft.com/en-us/sharepoint/customize-sharepoint-site-permissions

Here are information about privat vs. public:

https://sharepointmaven.com/public-vs-private-office-365-groups/

Regards, Dave