Our team has seen an influx of cases where Office Web Apps Server 2013 is functioning on a global scale (all workbook books are opening in the WOPIFrame), but for some reason (Unsupported Features) workbooks cannot be opened in the browser and the below message is thrown:
We have also seen these errors which is most likely something corrupt in the workbook (like a shape/object).
The question then arises, "Where are these Unsupported Features and what is the best method to locate these?" We do have a tool that can analyze the entire workbook:
Excel Services Compatibility Checker Add in - Beta
Note: Excel will need to be 32-bit and the Click to Run (in my experience) will not load this COM add-in. Download here.
If you do not see the add-in loaded when you launch Excel, you will need to go to (in Excel) File > Options > Add-ins > Manage: COM Add-ins > Go...
Choose Excel Services Compatibility Checker > OK
You will now see an Excel Services tab, you can now run a Server Compatibility Check to see where these Unsupported Features are.
Now you have proof there are a lot of Unsupported Features. If you want to remove all the Unsupported Features you can by clicking Quick Fix, but this will remove all unsupported features when this tool was built (2007). In most case the culprit is a (or several) shape(s)/object(s), but not all of them. You are probably asking yourself, "Ok, so how do I find which ones are bad?" I will do my best to explain what I have done. First off, you could have 10 worksheets and you don't want to remove all shapes/objects from the workbook, cause some could be benign. I like to pick the workbook apart sheet by sheet. To do this, right click on a sheet Move or Copy... > (new book) > Create a copy
Now upload that workbook (again, containing just one worksheet) to SharePoint. If that works, you know the culprit (Unsupported Feature - object/shape) is not in that worksheet. Move on to the next worksheet until you find one that does not load in the browser. Now, in Excel > Home tab > Find & Select > Go To Special > Objects
You will now see all Objects are selected in that workbook (the border will be selected). If you click the Delete key all the objects (and shapes) will be removed. You can then re-upload to SharePoint and test. If it opens, you know that an object/shape is the culprit. You will then need to step through each object (delete it and test) to see if you can isolate which object(s) are the culprit. It is rather lengthy and time consuming, but this is the best solution I have found and can help you from having to remove every object/shape from the workbook or rebuilding the workbook.
Differences between using a workbook in Excel and Excel Services
Excel Services part 12: Unsupported features
Excel Services in SharePoint 2010 Feature Support
Edit a workbook that contains features unsupported by Excel Web App