If you see HTTP 500 errors in browser console, for component JS and CSS resources like
/resource.ashx/636687137980000000/...js net::ERR_ABORTED 500 (Internal Server Error)
/resource.ashx/636687137980000000/...css:1 Failed to load resource: the server responded with a status of 500 ()
HTTP 500 problem may be caused by the user's own rules in Web.Config for URL Rewrite Module of IIS.
The solution is to add a top rule to prevent this:
<rewrite>
<rules>
<rule name="Stop Rewriting for GleamTech Handlers" stopProcessing="true">
<match url="(resource|filemanager|fileuploader|documentviewer)\.ashx" />
<action type="None" />
</rule>
.
.
.
</rules>
</rewrite>
Add this rule to the top of the rules and when the request is .ashx, it will stop processing your other rules so that the .ashx request passes through and works.
If you see HTTP 404 errors in browser console, for component JS and CSS resources like
/resource.ashx/636687137980000000/...js net::ERR_ABORTED 404 (Not Found)
/resource.ashx/636687137980000000/...css:1 Failed to load resource: the server responded with a status of 500 (Not Found)
If you examine IIS logs, you can see if the problem was being caused by urlscan. It may prevent the component js and css files from loading. Remove urlscan or configure it to allow those URLs.
Another reason may be this if you upgraded from older versions:
Ensure there is no old DLL file named GleamTech.Core.dll anywhere in your project, it was replaced with new DLL file named GleamTech.Common.dll since Version 7.3.0 - November 20, 2019
In Visual Studio: Go to Tools -> NuGet Package Manager -> Package Manager Console and run these commands one by one in order:
Uninstall-Package FileUltimate -RemoveDependencies
Uninstall-Package FileUltimate.NuGetOrg -RemoveDependencies
Install-Package GleamTech.FileUltimate
If you are using direct DLL references instead of NuGet reference, first clean your project, remove references to old assembly GleamTech.Core.dll, add references to new assembly and rebuild your project. Ensure there is no GleamTech.Core.dll left in your project bin folders.