We have a web application written in C# that connects to SharePoint Online to retrieve a list of all the sub sites and populates the drop down in the UI. But this drop down stopped populating in all the environments suddenly and shows the following error -
Error loading page: Search has encountered a problem that prevents results from being returned. If the issue persists, please contact your administrator.
As part of troubleshooting, verified the permissions of the service accounts, re-indexed the site so that it will be picked up for next scheduled crawl by Microsoft, debugged it locally and found that it is able to retrieve the first 500 results fine but with a subsequent call to get another set of 500 records is where it bombs. Is there anything else that I would need to check? Please advise.
Any help is greatly appreciated. Thank you in advance.