There are couple of options (see the end for reference) how to resolve this issue – this article walks you through using SharePoint Designer to resolve this issue. I personally find this option easier :-). Image 1
Here are the steps to resolve the issue:
- - List permissions page opens in the browser
- Add the necessary permission - SharePoint group which has full control to this site. Image 5
Have the owner test out now. This should resolve the access denied error. Hope this help!
Here is another approach to resolve this issue – even though this Microsoft KB talks about SharePoint Online; I was able to resolve on-premise issues following the approach.
"Access Denied" to Access Requests list or “Request approval failed” when you process a pending request in SharePoint Online