SharePoint permissions group has dissapeared from view

Question

I am a site owner. In the SharePoint Permissions page, there are several groups. I created a new group and added one user. The new group remained visible and accessible in the permissions page for a few days. Now it has disappeared from view and I can't edit it or add new members.

The sole person in the group has not lost access. When I select "Check Permissions", I see that he still has permissions through the new group.
The new group still exists but I can't access it.

I would like help in getting this group to re-appear in the permissions page so I can edit it

Answer 1

@Elba

Whether this newly created group disappear in the site permissions page or when you want to add users into this group, it shows "You do not have permission to view the membership of the group."?

Please go to SharePoint admin center -> Sites -> Active sites -> Select the site collection -> Permissions -> Make sure your account is the site admin. Then go to site permissions page to check whether you could see newly created group.

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