Use SharePoint Designer might be easier:
• Open up the site collection in SharePoint Designer 2013
• Navigate to the Access Requests list, right-click and select Properties
• Copy the List ID (including the opening and closing braces)
• In the browser address bar, enter https:///_layouts/15/ListEdit.aspx?List={GUID}, and then press Enter. (a sample URL looks like this: https://blabla.sharepoint.com/sites/TS14/_layouts/15/ListEdit.aspx?List={39F808F1-03FB-35C0-BA90-D12345EABCDE}
• On the List Settings page, click Permissions for this list.
• Make sure that the Owners group for the site is included in the list of permissions for the Access Requests list. If the Owners group for the site collection does not exist, click Grant Permissions, enter the name of the Owners group for the site in the Share dialog box, and then click Share.