When attempting to open an Access 2010 web database within a SharePoint Online environment, you may receive one of the following error messages:
“Site is down”
“An error has occurred”
“Failed to evaluate expression ‘<expression>’
The Product Group has reported that this issue should now be resolved for all tenants.
In some cases, you may need to make a design change in the Access client and then resync the web database in order to resolve the issue.