Troubleshooting: The File that You Are Trying to Use Is Too Large
If you are trying to upload a large image file that is larger than 30 MB, such as a high-resolution photo, Microsoft Dynamics NAV will give you an error message that says that the file that you are trying to upload is too large. This behavior can be changed by modifying the IIS configuration to support large file uploads.
Resolution
The IIS administrator should make the following changes in the Internet Information Services (IIS) Manager.
Launch IIS Manager.
In the left pane of IIS Manager, select the Microsoft Dynamics NAV web site, and choose Request Filtering.
In the Actions pane of the Request Filtering window, choose Edit Feature Settings.
Set the field Maximum allowed content length (Bytes) to an appropriate value, such as 100000000 and choose the OK button.
In the left pane of IIS Manager, select the Microsoft Dynamics NAV web site, and choose Configuration Editor.
In the Configuration Editor, make sure that the From field is set to Microsoft Dynamics NAV 2016 Web Client Web.config.
Set the Section field to system.web/httpRuntime and now several properties will appear.
Set maxRequestLength to an appropriate value, such as 100000 (kilobytes) and choose the Apply action on the right.
Close IIS Manager.
The new settings should take effect immediately without refreshing the IIS or the site.