Hi Marc,

Thank you for responding. We were able to resolve the issue over the weekend.

We found the null reference exception, but it was on a different template than what was being logged. Since I was unable to pull down the content to my local for troubleshooting, the Umbraco support person copied the home node in the content tree so that we could delete content in the copy without losing it. Once we completely removed the content related to the template throwing the exception, we started seeing a new exception on another template. When we looked into that template, we did find a null reference exception. Once that was fixed, the page started working again.

I talked to our client that manages the content and it sounded like they did make a change on that day, but I can't find any record of it in the audit history for that page. I'm still very confused about why there's no audit history and why the exception was showing up on another template, but we're running Umbraco 7.10, so maybe this is not an issue on newer versions. Even though this is already resolved, I'll document the errors and code in case this is beneficial to anyone going forward:

Here is the error message:

Message:
An unhandled exception occurred


Exception:
System.NullReferenceException: Object reference not set to an instance of an object.
   at ASP._Page_Views_graphicWithDetails_cshtml.Execute() in c:\home\site\wwwroot\Views\GraphicWithDetails.cshtml:line 23
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy()
   at System.Web.Mvc.WebViewPage.ExecutePageHierarchy()
   ...

Here is the template code. It's a partial used by a nested content doctype:

@inherits Umbraco.Web.Mvc.UmbracoTemplatePage<ContentModels.GraphicWithDetails>
@using ContentModels = Umbraco.Web.PublishedContentModels;
@{
    Layout = null;

    var cssClass = Ctl.Core.Helpers.NestedContentViewCssClass(Model.Content);
    var content = Model.Content.Content;
    if(content == null)
    {
        content = new HtmlString("");
    }
}


<div class="container pad @cssClass">
    @if (Model.Content.HasValue("Headline"))
    {
        <h2 class="section_headline">@Model.Content.Headline</h2>
    }

    <div class="graphic_with_details reverse_on_small">
        <div class="details right_spacing">
            @Html.Raw(content)
        </div>

        <div class="graphic">
            <img src="@Model.Content.Image.Url" alt="@Model.Content.Image.GetPropertyValue("alt")">
        </div>
    </div>
</div>

Other pages are/were working

We use Modelsbuilder, and I had regenerated models.

Umbraco version is 7.10.6