Sites tab in OneDrive(IOS) mobile app has an error "Make sure you're connected to a Wi-Fi or.."

Hi SPO Admin, 

Thank you for your response. We have re-installed and check the WLAN and Cellular settings, everything is okay. We can confirm that by seeing files on other tabs within the OneDrive app. The Sites tab was the only one has this error. 

We also followed the below steps from MS - How to add OneDrive for business account, however, it returned an error. 

1. Tap Add account.

2. On the sign in screen, tap Have a SharePoint Server URL? Then enter the web address of your SharePoint server to continue the sign-in process. The web address, also known as a URL, may look like http://portal.

Error: 

But when we browse the Sharepoint URL through mobile browser or SharePoint mobile app, we are able to get in.